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Frontiers in High-Energy Astroparticle Physics Karl Mannheim Universit¨a ts-Sternwarte Geismarlandstra?e 11D-37083G¨o ttingen Germany Abstract With the discovery of evidence for neutrino mass,a vivid gamma ray sky at multi-TeV energies,and cosmic ray particles with unexpectedly high energies,astroparticle physics currently runs through an era of rapid progress and moving frontiers.The non-vanishing neutrino mass establishes one smooth component of dark matter which does not,however,supply a critical mass to the Universe.Other dark matter particles are likely to be very massive and should produce high-energy gamma rays,neutrinos,and protons in annihilations or decays.The search for exotic relics with new gamma ray telescopes,extensive air shower arrays,and underwater/-ice neutrino telescopes is a fascinating challenge,but requires to un-derstand the astrophysical background radiations at high energies.Among the high-energy sources in the Universe,radio-loud active galactic nuclei seem to be the most powerful accounting for at least a sizable fraction of the extragalactic gamma ray ?ux.They could also supply the bulk of the observed cosmic rays at ultrahigh energies and produce interesting event rates in neutrino telescopes aim-ing at the kubic kilometer scale such as AMANDA and ANTARES.It is proposed that the extragalactic neutrino beam can be used to search for tau lepton appear-ance thus allowing for a proof of the neutrino oscillation hypothesis.Furthermore,a new method for probing the era of star formation at high redshifts using gamma rays is presented which requires new-generation gamma ray telescopes operating in the 10-100GeV regime such as MAGIC and GLAST.
1Introduction and practical de?nition of high-energy astroparticle physics
Central to modern astronomy is the dark matter problem and it is commonly believed that its solution will trigger major advances in particle physics and cos-mology [1].So far dark matter is only known through its gravitational e?ects,but the understanding of the nature and origin of dark matter requires to obtain more direct information about its mass and interactions.Cosmology and particle physics qualify weakly interacting massive particles (WIMPs)with masses between 100GeV and a few TeV as likely candidates.The WIMPs violently annihilate with their anti-particles in rare collisions or they could be unstable.These modes lead to secondary gamma rays and neutrinos which can be detected on Earth [2].The
suspected large WIMP mass then corresponds to gamma ray and neutrino energies in excess of100GeV.In addition to the dark matter particles,there may be other relics from the early Universe,such as quintessence,vacuum energy,or topolog-ical defects.Quintessence is a slowly rolling scalar?eld connected with massive bosons,and this could also lead high-energy phenomena,although no worked-out model exists to my knowledge.The recent discovery of accelerating expansion using SNIa as a tracer of cosmic geometry seems to make a strong case for quintessence [3,4].Similarly,if the scalar?eld has settled to some false(meta-stable)vacuum, the energy density of this vacuum could drive the deceleration parameter away from?/2.Topological defects preserve false vacuum in pointlike(monopoles), one-dimensional(strings),two-dimensional(domain walls),or higher dimensional space-time structures.They are topologically stable,but have a variety of ways to communicate to our world in addition to their gravitation.E.g.,they can dissipate into GUT-scale bosons(～1016GeV)which are unstable themselves and fragment into jets consisting of gamma rays,neutrinos,and protons at ultra-high energies [5].After their propagation through intergalactic space,electromagnetic cascading and secondary particle production shift most energy injected by these exotic pro-cesses to much lower energies where the energy release competes with that due to ordinary astrophysical sources.
In order to identify new physics phenomena,it is therefore of crucial impor-tance to obtain a complete inventory of the astrophysical high-energy sources which act as a background for these searches.This de?nes the high-energy astroparticle physics program from a practical point of view and follows the logic inherent to the general astronomical exploration of the sky to cover the entire range of wavelengths with comparable sensitivity.
Among the non-thermal sources in the Universe,radio-loud active galactic nu-clei(AGN)seem to be the most important energetically.There are other interest-ing sources,such as gamma ray bursts(GRB)and clusters of galaxies,but their non-thermal energy release does not come close that of AGN.There are some in-triguing complications arising through calorimetric e?ects,since the intracluster medium in clusters of galaxies surrounding AGN con?nes escaping relativistic par-ticles for some time and thereby gives rise to a secondary luminosity tied to the energy release of the AGN and the cooling time scale of the intracluster medium. The radio-loud AGN come in various disguises,depending on the orientation of their radio jet axes and the properties of the circum-nuclear matter in their host galaxies.The most extreme versions are radio galaxies with the radio jet axes almost in the plane of the sky and the blazars with the radio jets pointing close to the line of sight to the observer which leads to a dramatic?ux increase owing to special relativistic e?ects(the so-called Doppler boosting).In Sect.2it is argued that radio-loud AGN can be expected to produce the entire extragalactic gamma ray background from an energetical point of view.Owing to beaming statistics, the number of unresolved sources responsible for most of this background should not be too large.Indeed the?ux from the～50resolved sources in the?ux-limited EGRET sample already equals a sizable fraction(of the order of15%)of the extra-galactic background?ux.With the next-generation gamma ray telescopes MAGIC
[6](giant17m air-Cerenkov telescope)and GLAST[7](space-borne silicon strip detector)it will be possible to probe deeper into the astrophysical source popu-lation producing the extragalactic background below100GeV thereby narrowing the range of opportunity for particle physics models of exotic processes producing gamma rays.In fact,the gamma ray background below100GeV provides a good measure of the entire electromagnetic energy release during the history of the Uni-verse,since gamma rays from remote sources cascade down to the energy range below100GeV which is shown in Sect.3.It is pointed out in Sect.4that a MAGIC observing campaign for high-redshift gamma ray sources can be used to probe the era of star formation and the evolution of the optical-ultraviolet metagalactic ra-diation?eld back to redshifts of～5.
The recent discovery of multi-TeV emission from Mrk421and Mrk501[8],the measurement of their spectra using the HEGRA air-Cerenkov imaging telescopes [9],and the improved measurements of the extragalactic infrared background[10], make a strong point in favor of accelerated protons in extragalactic radio sources which is shown in Sect.5.The following Sect.6discusses the immediate implications that the radio-loud AGN could well produce the observed cosmic rays at highest energies and high-energy muon neutrinos.Finally,in Sect.7it is pointed out that the extragalactic muon neutrino beam is likely mixed with tau neutrinos[11]which leads to very interesting experimental signatures,such as the disappearance of the Earth shadowing e?ect at ultra-high energies and the appearance of tau leptons in underwater/-ice detectors.
2Origins of extragalactic background radiation Inspection of Fig.1shows an interesting pattern in the present-day energy density of the di?use isotropic background radiation consisting of a sequence of bumps each with a strength that is decreasing with photon energy.The microwave bump is recognized as the signature of the big bang at the time of decoupling with its energy density given by the Stefan-Boltzmann law u3K=aT4.The bump in the far-infrared is due to star formation in early galaxies,since part of the stellar light,which is visible as the bump at visible wavelengths,is reprocessed by dust obscuring the star-forming regions.The energy density of the two bumps can be inferred from the present-day heavy element abundances.Heavy elements have a mass fraction Z=0.03of the total mass densityρ?and were produced in early bursts of star formation at redshift z f by nucleosynthesis with radiative e?ciency ?=0.007yielding
ρ?Z?c2
u ns～
1+z f
0.01
log 10 photon energy [eV]-7.0-6.0
-5.0
-4.0-3.0-2.0-1.0
0.0
l o g 10 [ε2
n (ε) / e V c m -3]Extragalactic radiation background
2
Fig.1:Sketch of the present-day energy density of the extragalactic
radiation background from radio waves to gamma rays.The dashed
line shows the expected AGN contribution to the low-energy di?use
background from the average quasar spectral energy distribution.
ing over a fraction of t agn /t ?～10?2of their lifetime implying that the electromag-netic radiation released by the accreting black holes amounts to
u accr ～
?accr M bh t ?
u ns ～1.4×10?4eV cm ?3(3)adopting the accretion e?ciency ?accr =0.1and the black hole mass fraction M bh /M ?=0.005[12].Most of the accretion power emerges in the ultraviolet where the di?use background is unobservable owing to photoelectric absorption by the neutral component of the interstellar medium.However,a fraction of u x /u bh ～20%taken from the average quasar spectral energy distribution [13]shows up in hard X-rays due to coronal emission from the accretion disk to produce the di?use isotropic X-ray background bump with u x ～2.8×10?5eV cm ?3(4)
[14].
Jets with non-thermal γ-ray emission show up only in the radio-loud fraction ξrl ～20%of all AGN and their kinetic power roughly equals the accretion power
[15].Hence one obtains for the background energy density due to extragalactic jets
u j =
ξrl 0.2
2.8×10?5eV cm ?3(5)If unresolved extragalactic jets are responsible for the di?use gamma ray back-ground,this requires a particle acceleration e?ciency given by
ξacc =u acc ξrad u j (6)
where u j denotes the total (kinetic +magnetic +randomized relativistic particle)energy density in extragalactic jets.Inserting the energy density of the observed extragalactic gamma ray background 1one obtains a limit for the acceleration e?-ciency
ξacc ≥0.18ξ?1
rad ξrl
(1?μ)(1+z )2E ～1 1+z
30GeV ?1eV (μ=0)(8)
where μdenotes the cosine of the scattering angle [18].The γ-ray attenuation e ?τdue to pair production becomes important if the mean free path λbecomes smaller than l ,i.e.if the optical depth across the line of sight through a sizable fraction of the Hubble radius obeys τ=l/λ≥1.For the computation of τone ?rst needs to know the pair production cross section
σγγ=3σT
1?β
(9)
where β= H ?[(1+z )ˉE (z )]?1to compute the line integral from z =0to some z =z ?.For a cosmological model with ?=1and Λ=0the function ˉE (z )simpli?es to (1+z )3/2.Hence one obtains the optical depth
τγγ(E,z ?)= z ?0dz dl 2 ∞
?th
d?n b (?)(1+z )3σγγ(E,?,μ,z )
=c 2 ∞
?th
d?n b (?)σγγ(E,?,x ?1,z )(10)
log 10 ε [eV]-5.0-4.0
-3.0-2.0-1.0
0.0
ε2
n (ε) [e V c m -3]Fig.2:The di?use isotropic microwave-to-ultraviolet background.
Solid curve:10th order polynomial interpolation of observational
data ([20,22,21],and references in [16]).
adopting a non-evolving present-day background density n b ,i.e.n ′
b (z,?′)d?′=(1+
z )3n b (?)d?where the dash indicates comoving-frame quantities.The simplifying assumption that the photon density transforms geometrically corresponds to the situation in which an initial short burst of star formation at z f >z ?produced most of the di?use infrared-to-ultraviolet background radiation.This simple assumption is replaced by a more realistic one in Sect.4.Fig.2shows the spectrum of the low-energy di?use background used to solve Eq.(10)numerically.
Figure 3shows the resulting τ(E,z )=1(omitting the subscript hereafter)curve for the microwave-to-ultraviolet di?use background spectrum shown in Fig.2.It is obvious that γ-rays above ～10?50GeV cannot reach us from beyond redshifts of z =z f =2?4.Higher energy γ-rays can reach us only from sources at lower redshifts (e.g.γ-rays with energies up to 10TeV have been observed from Mrk 501at z =0.033in accord with Fig.3[22]).
Corollary I:If the extragalactic gamma ray background originates from unre-solved sources distributed in redshift similar to galaxies,its spectrum must steepen above ～30GeV due to γ-ray pair attenuation.
Here is has been tacitly assumed that the γ-rays which have turned into electron-positron pairs do not show up again.This is,in fact,not quite true,since the pairs are subject to inverse-Compton scattering o?the microwave background thereby replenishing γ-rays.The 2.7K background is more important as a target than the shorter wavelength background,since there is no threshold condition for Thomson scattering contrary to pair production and since 2.7K photons greatly outnumber
10.011.012.013.014.0
15.016.017.0
log 10 E [eV]-6.0-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
l o g 10 z Fig.3:The γ-ray horizon τ(E,z )=1for the low-energy background
spectrum shown in Fig.2.Cosmological parameters are h =0.6,
?=1,and ?Λ=0.For a general discussion of pair attenuation,see
reference [23].
the latter.The inverse-Compton scattered microwave photons turn into γ-rays of energy E ic ～10 1+z 30GeV
2MeV (11)conserving the energy of the absorbed γ-ray which corresponds to a constant E 2dN/dE ,i.e.the expected slope of the di?erential spectrum is about -2(-2.1observed).A small amount of energy is lost to lower frequency synchrotron emis-sion,if magnetic ?elds are present in the interagalactic medium.
Corollary II:Energy conservation in the reprocessing of γ-rays from higher to lower energies by pair production and subsequent inverse-Compton scattering produces an approximate dN/dE ∝E ?2power law extragalactic gamma ray back-ground between ～10MeV and ～30GeV.
4Evolution of the metagalactic optical-ultraviolet ra-
diation ?eld
4.1A simple model based on the observed ”e?ective”star forma-
tion rate
Consider an e?ective
2cosmic star formation history ˙ρ?(z )denoting the production rate per unit volume of mass which has formed to stars at a redshift of z.Such star formation histories have been inferred from galaxy counts in the Hubble Deep Field
[24].Since the present-day infrared background is strong enough to aborb gamma rays in the TeV range in the local Universe far from the peak of the star formation history,its evolution in the past is rather irrelevant in this context.However,the present-day optical radiation background scaled back to the peak of the star forma-tion history at a redshift of z b ～1.5implies gamma ray attenuation in the 20GeV regime from sources at this redshift.Over this distance scale the evolution of the background becomes important,since it is gradually produced by the forming stars.For the gamma ray attenuation only the evolution of the number density n (?,z )d?of the background photons is important which relates to the photon production rate ˙n ∝˙ρ/?in the following way:
n (?,z )d?= z f
z dz ′˙n (?′,z ′)dt 1+z
?3d?′(12)
The evolving background must be normalized to yield the observed present-day radiation background
n (?,0)d?= z f 0dz ′˙n (?′,z ′)dt
?
∝(1+z )α?1(15)with α=αM =3.8for 0≤z ≤1.5=z b and α=βM =?4.0for z b =1.5≤z ≤10=z f .We also investigate a star formation rate which exhibits a plateau beyond z b .
Equation (1)enters the formula for the gamma ray optical depth:
τ(E ?,z )=
z 0dz dl 2The term “e?ective”means that only the star formation rate inferred from photons which have made it through possible obscuring dust clouds are of relevance for the build-up of a metagalactic radiation ?eld.
Note that cosmology enters through dl/dz(which depends on?,?Λ,and H?), not through n(?,z)for a given parametrization of˙ρ?(z).However,the parametriza-tions˙ρ?(z)must also satisfy observational constraints such as number counts and the present-day di?use background which themselves depend on cosmology.Turn-ing this around it means that one must?nd the cosmology parameters for which a measured gamma ray horizon(i.e.,the curveτ(E?,z)=1)and the star formation history data come into mutual consistency.
The gamma ray horizon from Eq.(16)is shown in Fig.4using the low-energy background spectrum template shown in Fig.2.The template was used to normal-ize the evolving background such that is identical to the template at z=0and scales to higher redshifts acording to Eq.(12).The fact that there is a redshift with a maximum star formation is very important.If power law evolution of the background emissivity were to continue all the way in the past,one could easily infer power law solutions for the scaling of n(?,z)which are more shallow than (1+z)3as in ref.[16],but such solutions become unrealistic beyond z b.
4.2Extragalactic gamma ray background
The origin of the observed di?use isotropic gamma ray background is unknown. The spectral shape and?ux density suggest that unresolved faint radio loud AGN are responsible for this background,similar to the situation in the X-ray band where deep observations have revealed that faint AGN are responsible for more than90%of the background emission.The EGRET-type radio-loud AGN seem contribute not more than～25%[25]to the extragalactic gamma ray background. The uncertainties about the faint end of the gamma ray luminosity function in the EGRET band allow for a larger contribution from the general class of radio-loud AGN.According to beaming statistics,the?ux-limited EGRET sample of AGN is dominated by highly beamed sources with a rather?at luminosity function.A much fainter,less beamed population with a steeper luminosity function is likely to?ll in the remaining75%,at least this seems very plausible considering the energetics of radio jets as was shown in Sect.2.I strongly expect that the?at-spectrum/steep-spectrum classes are mirrored in di?erent populations of gamma ray sources.The nearest steep-spectrum radio sources would have been detected by EGRET even if they were faint(with their gamma ray luminosity roughly a factor of～50larger than the5GHz luminosity).However,with a lower compact-ness for instrinsic gamma ray absorption∝L/R the steep-spectrum radio sources could emit most of their gamma ray power above the EGRET range.It is up to new air-Cerenkov telescopes with threshold energies above10GeV and GLAST to probe this proposal.
If the extragalactic jets are indeed responsible for most of the gamma ray back-ground,it is straightforward to investigate the e?ect of pair attenuation on the spectrum of the background.The precise shape of the spectra of the individual sources at high redshifts is rather unimportant owing to the e?ects of cascading discussed in Sect.3.Adopting a power law gamma ray spectrum per source with
012
345
redshift z 1011
12
p h o t o n e n e r g y l o g 10 E [e V ]The cosmological gamma ray horizon
?=1; ?Λ=0; h=0.5; z b =1.5; z f =10, α=3.8; β
=-4.0 (CDM)
Fig.4:Gamma ray horizon due to interactions with an evolving
metagalactic radiation ?eld as computed from the e?ective star for-
mation rate.Sources below the horizon curve su?er no signi?cant
pair-attenuation along the line of sight.The grey band indicates the
uncertainty of the horizon as estimated from the range of interpola-
tions allowed between observational upper and lower bounds of the
?ux of the present-day optical-UV di?use background.Note that
the metagalactic radiation ?eld before the maximum of the cosmic
star formation rate (indicated by the dashed line)is too weak to
signi?cantly attenuate gamma rays below 20-40GeV resulting in a
near-constant optical depth.The light solid line shows the e?ect of
a star formation rate with an extended plateau which causes the op-
tical depth to continue to grow with redshift beyond z =1.5.The
horizontal lines indicate the e?ective threshold energies for various
air-Cerenkov telescopes.It is emphasized that triggering below 20-
40GeV,which can be achieved by the MAGIC telescope,is crucial
for probing the star formation era.Such an investigation is comple-
mentary to studies of galaxies at high redshifts,since it is addition-
ally sensitive to di?use sources of optical-UV photons such as would
be arising from exotic particle decays (one possible scenario for the
reionization epoch).
the average slope of the resolved EGRET sources
dN
E1 ?2.1(17) extending from E1=10MeV to E2=1TeV and taking into account the luminosity density evolutionΨ(z)of AGN,we obtain a good approximation of the present-day background energy density
u(E)=
4π
dz
Ψ(z)(1+z)?4B E(1+z)E2C[E,z](19) where dt/dz is given by
dt/dz=
1
?(1+z)3+(1????Λ)(1+z)2+?Λ
(20)
and the function C[E,z]for the e?ect of pair attenuation can be approximated as
C[E,z]=e?E
log 10 E [eV]-7.0-6.0
l o g 10 E d u /d E [e V c m -3]Extragalactic radio sources
diffuse gamma ray background
Fig.5:The gamma ray horizon enforces a shallow turnover beyond ～
30GeV in the spectrum of the extragalactic gamma ray background
which is only weakly dependent on cosmology (results from further
investigations by T.Kneiske will soon be reported elsewhere.).
if it is not the radio sources themselves,some other source must be able to pro-duce a relativistic proton distribution with an enormous energy ?ux reaching these ultrahigh-energies.It has been suggested that GRBs may do that,but there are strong arguments against that proposal presented in Sect.6.Here we concentrate on the consequences of accelerating baryons in radio jets to these extremely high energies where radiative losses become important.A few years ago,a model coined the proton blazar model has been presented in which accelerated protons have been assumed in addition to the accelerated electrons [27].This model made de?nite predictions about the multi-TeV spectra of nearby blazars [28]which can now be compared with observations of Mrk 501and Mrk 421obtained with the HEGRA air-Cerenkov telescopes.In fact,this was the only model prior to the observations which made any quantitative prediction of multi-TeV emission from these sources.
An important,although not necessary,assumption of the original model is that the magnetic ?eld pressure energy density is in equipartition with that in relativistic particles implying that synchrotron cooling dominates over Compton cooling (since the photon energy density remains below that in particles).This a?ects accelerated electrons as well as secondary electrons at ultrahigh-energies.Evaluating a simple conical jet geometry shows that typical blazars are optically thin to gamma rays up to the TeV range.Unsaturated synchrotron cascades initiated by accelerated protons interacting with the synchrotron photons from the accelerated electrons are computed as the stationary solution of a coupled set of kinetic equations which is then Doppler boosted to an appropriate observer’s frame.A series solution is
found employing Banach’s?xed point theorem which can be physically interpreted as a series of superimposed cascade generations.The cascade generation of gamma rays emerging in the TeV range on the optically thin side has a spectral index s～1.7(di?erential spectrum I?)steepening byα=0.5?0.7above TeV.The indexαis the energy index of the optical synchrotron photons which act as a target for both gamma rays and protons.The reason for the break is the onset of intrinsic pair attenuation characterized by the escape probability Iγ=P esc I?for a homogeneously mixed absorber and emitter
P esc=1?exp[?τ(E)]
τ(E)
∝E?αforτ?1(22)
The shape of the multi-TeV spectrum is therefore not sensitive to changes in the maximum energy and can remain constant under large-amplitude changes of the ?ux associated with changes in the maximum energy.
The observed multi-TeV spectrum is modi?ed by the quasi-exponential pair attenuation due to collisions of the gamma rays with photons from the infrared background.A recent evaluation of this background based on direct measurements obtained from COBE data in the far-infrared,and inferred as a lower limit from number counts based on ISO observations of the HDF shows that this e?ect com-pensates the shallow downward curvature discovered by the HEGRA collaboration in the spectrum of Mrk501[9].If the gamma rays were due to inverse-Compton scattering,the shallow curvature is di?cult to understand for a number of rea-sons given in ref.[22].The most important of them is that one must expect the accelerated electrons not to be able to reach energies much higher than10TeV. An inverse-Compton spectrum produced by these electrons would therefore have to show signi?cant curvature approaching this maximum energy adding to the in-evitable curvature due to gamma ray interactions with the infrared background photons.There are some rumours that quantum gravity e?ects could possibly sup-press pair production over intergalactic distances,but that remains highly specula-tive.I consider the agreement between the proton blazar prediction and observation very promising for the model,albeit minor discrepancies must be expected,since the proton blazar model is highly simpli?ed in order to avoid too many free pa-rameters and to be predictive.Therefore I take the freedom to speculate about the emissions associated with the gamma rays,viz.cosmic rays and high-energy neutrinos in the following sections.
6Neutrino and cosmic ray predictions
The photo-production of pions leads to the emission of neutrons and neutrinos. The neutrons decay to protons,and such extragalactic cosmic rays su?er energy losses traversing the microwave background[29].At an observed energy of1019eV, the energy-loss distance isλp～1Gpc owing to pair production.This distance corresponds to a redshift z p determined byλp=(c/H?) z p0dz/[(1+z)ˉE(z)]where ˉE(z)= ?(1+z)3+?R(1+z)2+?Λ 1
0.00.5 1.0 1.5
log 10 E [TeV]
-4-3
-2-101
l o g 10 F γ [10-11/(T e V c m 2 s )]
Fig.6:Comparison of predicted and observed ?ux density spectrum
in the multi-TeV range for Mrk 501.The thin solid line shows the
spectrum published in [28].The upper thick solid lines show this
spectrum scaled to the 300GeV ?ux levels during the two obser-
vation epochs where the air-Cerenkov data indicated by the solid
and open symbols were obtained with the HEGRA telescopes.The
dashed line shows the spectrum without the e?ect of the assumed
marginal interagalactic gamma ray attenuation due to interactions
of the gamma rays with metagalactic infrared radiation.More re-
cent HEGRA observations with higher statistical signi?cance show
some downward curvature in the 10TeV range which may be at-
tributed to a stronger attenuation which is in line with new analyses
of COBE data and ISO galaxy counts in the Hubble Deep Field [10].
where h 50=H ?/50km s ?1Mpc ?1.Therefore,when computing the contribution of extragalactic sources to the observed cosmic ray ?ux above 1019eV,only sources with z ≤z p must be considered.Assuming further that extragalactic sources of cosmic rays and neutrinos are homogeneously distributed with
a monochromatic
luminosity
density Ψ(
z )∝(1+z )3+k where k ～3for AGN [30],their contribution to the energy density of a present-day di?use isotropic background is given by
u (0)= z m
0Ψ(z )(1+z )?4dl H ? z m 0(1+z )k dz
u p (0)=ξ z m 0(1+z )k ?2/ˉE
(z )dz 3
A recent paper by Waxman and Bahcall [32]refers to the neutrino ?ux from model
B in the original work which was given only to demonstrate that hadronic jets cannot produce a di?use gamma ray background with an MeV bump (as measured by Apollo and which is now known to be absent from a COMPTEL analysis)without over-producing cosmic rays at highest energies.
Fig.7:Comparison of proton(solid line)and neutrino?uxes(dotted
lines,from top to bottomνμ,ˉνμ,andνe)from the proton blazar
model(Monte-Carlo computations and?gure by R.J.Protheroe).
The open symbols represent the observed cosmic ray?ux.
di?cult to predict due to their unknown magnetic?elds and turbulence level.The reason for the low rate is that the neutrino spectrum is extremely hard,a di?erential proton spectrum of index s p=2photo-producing pions in a synchrotron photon target also with di?erential index s syn=2yields a di?erential neutrino spectrum of index sν=1(dN/dE∝E?s)up to some very high energy.The spectrum may be more shallow,if the target photons have a spectral index of0.7as suggested for Mrk501,thereby increasing the number of lower energy neutrinos while keeping the bolometric?ux the same.Because of the long lever arm from106.5TeV to 1TeV,a factor of～100increase in the event rate would result from this e?ect.
At this point the discovery of neutrino mass announced by the Super-Kamiokande collaboration[11]comes in changing the situation in a major way.A de?cit of at-mospheric muon neutrinos was observed with Super-Kamiokande at large zenith angles with the most likely explanation being a full-amplitude oscillation of muon ?avor eigenstates to tauon?avor eigenstates across the Earth at GeV energies. While this would make long-baseline experiments searching for the appearance of the tauon in a muon neutrino beam with laboratory beams extremely di?cult(if not impossible),it quali?es the expected extragalactic sources of muon neutrinos as an ideal neutrino beam.The energies are high enough to produce tauons on the mass-shell and the distance large enough to obtain full mixing.Since tauons de-cay before interacting in the Earth and since the Earth is opaque to tau neutrinos above～100TeV,a fully mixed extragalactic muon neutrino beam must initiate tauon cascades in the Earth shifting the tauon neutrino?ux down to energies of ～100TeV[35]and obliterating the Earth-shadowing e?ect[36]that makes the
muon solid ange very narrow at high energies.
The neutrino oscillations would have another important consequence.Current data suggested a maximal mixing between muon and tauon?avors and a mass di?erence given by
?m2μτ=m2ν
τ?m2ν
μ
=5×10?3eV2(25)
The mass di?erence between electron and muon?avored neutrinos inferred from the solar neutrino de?cit is orders of magnitude less,and this implies that the neutrino masses could be highly degenerate if they are at the eV https://www.doczj.com/doc/bc934721.html,ing the limit mν
e
<5eV,the maximum allowed combined neutrino mass would be
mν≈3mν
e
<15eV.(26) Inserting this into the Cowsik-McClelland bound one obtains the maximum con-tribution to the(hot)dark matter of the Universe
?ν<15
0.65 ?2.(27)
Due to free streaming of the neutrinos at the time of recombination,density?uc-tuations of this dark matter component would be wiped out on scales less than
λν=30(h/0.65)?2Mpc(28) and would therefore have no consequence for the dark matter inferred from studies of galaxy halos or galaxy clusters which yield?=0.3±0.1[37].Structure formation simulations exclude?νto be larger than0.15[38]which is in agreement with the above upper limit and both evidences together rule out neutrinos as the dark matter which could supply a critical mass to the Universe.
8Discussion and summary
The paper highlights in a personally biased way on a few developments in high-energy astroparticle physics,rather than to give a review of all the activities in the ?eld which encompass a much wider scope from the origin of cosmic rays to quan-tum gravity and which involve a truly impressive number of experimental e?orts. From my point of view,the identi?cation of one component of dark matter using the discovery of the atmospheric neutrino anomaly with Super-Kamiokande repre-sents a major achievement,and I have highlighted its consequence that neutrinos cannot close the Universe.Furthermore,this discovery is not su?cient to prove the neutrino oscillation hypothesis conclusively.An experiment is needed which shows the appearance of the tau lepton in a beam of muon neutrinos,and I have shown that neutrinos due to proton acceleration in extragalactic sources would be ideally suited as a beam for a tau-appearance experiment in one of the major neutrino telescopes which are under construction.From an astrophysical point of view,the oscillations are also important for another reason,since they remove the Earth shadowing e?ect which suppresses the response of a neutrino telescope to
extraterrestrial sources of very high-energy neutrinos.This makes the discovery of neutrinos from radio-loud AGN much more probable in a few years.
Other kinds of dark matter such as right-handed neutrinos,supersymmetric par-ticles,magnetic monopoles,or other topological defects and their associated gauge bosons,are likely to be very massive.It is a formidable task to?nd other than grav-itational evidence for this dark matter due to the electromagnetic(photons),weak (neutrinos),and strong(protons)couplings of its decay and annihilation products. Inevitably this task requires to understand all the astrophysical background radi-ations at high energies.The astrophysics governing this energy domain itself has proven to be a fascinating realm.A good example is the discovery of multi-TeV emission from nearby blazars using the HEGRA imaging air-Cerenkov telescopes. The observational?ndings frustrate the worldwide elite in theoretical astrophysics and seem to provide key insights into the extraordinary physics driven by weakly accreting black holes.
If the recent determinations of the infrared background from ISO galaxy counts (lower limits)and COBE/DIRBE and FIRAS are correct,then the steepening in the multi-TeV spectrum of Mrk501observed with the HEGRA air-Cerenkov telescopes is due to the predicted gamma ray attenuation in collisions with these infrared background photons.Predictions of the attenuation process for sources at higher redshifts depend strongly on the evolution of the metagalactic optical-UV radiation?eld.It will therefore soon be possible to independently probe the star formation history using10-100GeV gamma rays from extragalactic high-redshift sources when lower threshold gamma ray telescopes such as MAGIC and GLAST are available.The method is sensitive to truly di?use photons between the galaxies and,when compared with calculations based on the observed star formation rate in early galaxies,allows to test the hypothesis whether the background photons originate from the stars or other sources(possibly connected with the reionization epoch).
The multi-TeV spectra from nearby blazars prediced on the basis of the proton blazar model are in accord with the observations if the e?ect of pair attenuation due to the extragalactic infrared background is taken into account.This is surprinsing, since the model gives stationary spectra,whereas the observed?ux is highly vari-able.Nevertheless,the spectra seem to remain rather constant in the multi-TeV domain.There are several properties which are not explained in the framework of a stationary quasi-homogeneous model by contruction,such as the apparently di?erent variability pattern of Mrk421in the GeV and TeV ranges.This does not argue against the proton acceleration hypothesis,since one could construct inhomo-geneous,non-stationary models to explain this phenomenology.The same is true for the problem of short-term variability,which may require to describe the pas-sage of shocks traveling through narrowly-spaced inhomogeneities.It is amazing, however,that a general feature expected from models based on electron acceler-ation is certainly not seen in the data of Mrk501,viz.the change of the upper cuto?energy with varying?ux.This can only mean that the cuto?is indeed due to intergalactic attenuation and that the electron maximum energy is much higher
than20TeV which is di?cult to understand in the presence of synchrotron and inverse-Compton losses.Another peculiar?nding is that the multi-TeV emission in Mrk501is accompanied by100keV synchrotron photons in some epoches,but not in all of them.Moreover,in Mrk421100keV synchrotron?ares have not been observed in spite of?aring TeV emission.So the story is not simple and likely to continue,brainstorming is always desired when confronted with a new phenomenon.
An interesting corollary from hadronic models of extragalactic gamma ray sources is that they would also emit cosmic rays and neutrinos at about equal luminosities(within a factor of a few).If the cosmic ray?ux emitted by hadronic accelerators equals that of the observed cosmic rays above1019eV,the associated gamma ray power from these sources is enough to produce the observed extra-galactic gamma ray background above about100MeV.The gamma ray power is larger than that in cosmic rays,since the cosmic rays lose energy traversing the low-energy background radiation?elds and most sources have high redshifts.It has been proposed in ref.[39]that GRBs are responsible for the highest energy cosmic rays,but more recent GRB observations indicate that most of them have high redshifts which is expected if they trace star formation.The strong evolution of the GRB luminosity density would then rule out GRBs as possible sources of the highest energy cosmic rays,since their cumulative gamma ray?ux is far be-low the putatively extragalactic gamma ray?ux.Although the muon event rate in neutrino telescopes from hadronic extragalactic gamma ray sources supplying the highest energy cosmic rays is low,neutrino oscillations lead to tau cascades canceling the Earth shadowing e?ect thereby increasing the detection probability. Tau lepton appearance in the neutrino telescopes would constitute the?rst direct measurement of the tauon(which so far has only been inferred from momentum conservation)and would prove the neutrino oscillation hypothesis. References
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JOIN IN 学生用书1 Word List Starter Unit 1.Good afternoon 下午好 2.Good evening 晚上好 3.Good morning 早上好 4.Good night 晚安 5.Stand 站立 Unit 1 6.count [kaunt] （依次）点数 7.javascript:;eight [eit] 八 8.eleven [i'levn] 十一 9.four [f?:] 四 10.five [faiv] 五 11.flag [fl?g] 旗 12.guess [ges] 猜 13.jump [d??mp] 跳 14.nine [nain] 九 15.number ['n?mb?] 数字 16.one [w?n] 一 17.seven ['sevn] 七 18.six [siks] 六 19.ten [ten] 十 20.three [θri:] 三 21.twelve [twelv] 十二 22.two [tu:] 二 23.your [ju?] 你的 24.zero ['zi?r?u] 零、你们的 Unit 2 25.black [bl?k] 黑色26.blue [blu:] 蓝色 27.car [kɑ:] 小汽车 28.colour ['k?l?] 颜色 29.door [d?:] 门 30.favourite [feiv?rit]javascript:; 特别喜爱的 31.green [gri:n] 绿色 32.jeep [d?i:p] 吉普车 33.orange ['?:rind?] 橙黄色 34.pin k [pi?k] 粉红色 35.please [pli:z] 请 36.purple ['p?:pl] 紫色 37.red [red] 红色 38.white [wait] 白色 39.yellow ['jel?u] 黄色 Unit 3 40.blackboard ['bl?kb?:d] 黑板 41.book [buk] 书 42.chair [t???] 椅子 43.desk [desk] 桌子 44.pen [pen] 钢笔 45.pencil ['pensl] 铅笔 46.pencil case [keis] 笔盒 47.ruler ['ru:l?] 尺、直尺 48.schoolbag [sku:l] 书包 49.tree [tri:] 树 50.window ['wind?u] 窗、窗口 Unit 4 51.brown [braun] 棕色 52.cat [k?t] 猫
小学英语自我介绍简单七篇 小学的时候我们就开始学习英语了,用英语进行自我介绍是我们值得骄傲的哦,以下是小编为大家带来的小学英语自我介绍简单,欢迎大家参考。 小学英语自我介绍1 Goodafternoon, teachers! Today, I`m very happy to make a speech here. Now, let me introduce myself. My name is ZhuRuijie. My English name is Molly. I`m 12. I come from Class1 Grade 6 of TongPu No.2 Primary School. I`m an active girl. I like playing basketball. Because I think it`s very interesting. I`d like to eat potatoes. They`re tasty. My favourite colour is green. And I like math best. It`s fun. On weekend, I like reading books in my room. I have a happy family. My father is tall and strong.My mother is hard-working and tall, too. My brother is smart. And I`m a good student. My dream is
to be a teacher, because I want to help the poor children in the future. Thank you for listening! Please remember me! 小学英语自我介绍2 Hello,everyone,Iamagirl,mynameisAliceGreenIaminClasstwoGrad efive,Iamveryoutgoing,Icandomanyhousework,suchascooking,swe epingthefloor,andIlikesinginganddancing,IamgoodatpiayingSoc cer,IhopeIcanmakegoodfriendswithyou.Thankyou! 小学英语自我介绍3 Hi, boys and girls, good morning, it is my plearsure to take this change to introduce myself, my name is ---, i am 10 years old. About my family, there are 4 people in my family, father, mother, brother and me, my father and mother are all very kind, welcome you to visit my family if you have time! I am a very outgoing girl(boy), I like reading、playing games and listening to music, of course, I also like to make friends with all the
Join In剑桥小学英语(改编版)入门阶段Unit 1Hello,hello第1单元嗨,嗨 and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 the pictures. 2 再听一遍给图画编号. up "hello" hands down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A ,what's yourname 3 一首歌嗨,你叫什么名字 Hello. , what's yourname Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字嗨,嗨. Hello, what's yourname I'm Toby. I'm Toby. Hello,hello,hello.嗨, 你叫什么名字我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. , what's yourname I'm 'm Toby. 嗨.嗨.嗨, 你叫什么名字我叫托比.我叫托比. Hello,hello,hello. I'm 'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name I'm Bob. 你叫什么名字我叫鲍勃. What's your name I'm Rita. What's your name I'm Nick. 你叫什么名字我叫丽塔. 你叫什么名字我叫尼克. What's your name I'm Lisa. 你叫什么名字我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,:What's this Pi:嗨,帕特.Pa:这是什么 Pi:My new :Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
小学生英语自我介绍演讲稿五篇 小学生英语自我介绍演讲稿（1） Good afternoon, teachers! My name is YangXiaodan. I`m 11 now. I`m from Class2 Grade 5 of TongPu No.2 Primary School. My English teacher is Miss Sun. She`s quiet and kind. She`s short and young. My good friend is ZhangBingbing. She`s 12. She`s tall and pretty. We`re in the same class. We both like English very much. I like painting , listening to music, playing computer games and reading books. My favourite food is chicken. It`s tasty and yummy. I often do my homework and read books on Saturdays. This is me. Please remember YangXiaodan. Thank you very much! 小学生英语自我介绍演讲稿（2） Hi everybody, my name is XX ,what’s your name? I’m 11 years old, how old are you? My favourite sport is swimming, what’s your favourite sport? My favourite food is hamburgers,what food do you like?
Join In剑桥小学英语(改编版)入门阶段 Unit 1Hello,hello第1单元嗨,嗨 1.Listen and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do itagain.Stand up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 2.listen again.Number the pictures. 2 再听一遍给图画编号. 1.Stand up 2.Say "hello" 3.Slap hands 4.Sit down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A song.Hello,what's yourname? 3 一首歌嗨,你叫什么名字? Hello. Hello.Hello, what's yourname? Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字? 嗨,嗨. Hello, what's yourname? I'm Toby. I'm Toby. Hello,hello,hello. 嗨, 你叫什么名字? 我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. Hello.Hello, what's yourname? I'm Toby.I'm Toby. 嗨.嗨.嗨, 你叫什么名字? 我叫托比.我叫托比. Hello,hello,hello. I'm Toby.I'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name? I'm Bob. 你叫什么名字? 我叫鲍勃. What's your name ? I'm Rita. What's your name ? I'm Nick. 你叫什么名字? 我叫丽塔. 你叫什么名字? 我叫尼克. What's your name ? I'm Lisa. 你叫什么名字? 我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,Pat.Pa:What's this? Pi:嗨,帕特.Pa:这是什么? Pi:My new skateboard.Pi:Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
小学生英文自我介绍及故事(精选多篇) 第一篇：小学生英文自我介绍 good afternoon everyone! my name is max. my chinese name is dong li zhen. i am six years old. i am in the primary school of jinling high school hexi branch.my family have four people. one,myfather, his name is dongning, he is a worker; two,my mother, her name is liqing,she is a housewife; three,my pet yoyo ,he is a dog; there is one more. now let me see….oh,yes,that is me! i love my family. i have many toys,a car ,a helicopter, two balls, three jumpropes. i like jumpropes best of all,because i jumprope very good. i have a pencilcase ,it’s bule. i have an brown eraser. i have five pencils,they are many colors, and one ruler,it’s white. i like english,i like speak english thank you! 第二篇：小学生英文自我介绍 自我介绍 各位老师好，我叫邵子豪，今年15岁，现在是红星海学校初中二年级学生。 我是一个善良、自信、幽默、乐于助人的阳光男孩，平时我喜欢和同学一起打篮球，还喜欢和爸爸谈古论今，我自引以为豪的是我有一个善解人意的妈妈和博学多才的爸爸，我为我生活在这样一个充满爱和民主的家庭中感到幸福！ hello , teachers: mynameisshaoziha o. i’mfifteenyearsold. istudy in hongxinghaimiddeleschool..iamingradetwonow. iamakind,confident,humourousandhelpfulboy..ilikeplaying basketballwithmyfriends. andialsoliketotalkaboutthehsitoryandthecurrent newswithmyfather. i amveryproudofmyfatherandmymotherbecauseoftheirknowledge.
五年级下英语月考试卷-全能练考-Join in剑桥英语 姓名：日期：总分：100 一、根据意思，写出单词。（10′） Fanny:Jackie, ________[猜] my animal,my ________最喜欢的 animal.OK? Jackie:Ok!Mm…Has it got a nose? Fanny:Yes,it’s got a big long nose,…and two long ________[牙齿]. Jackie:Does it live in ________[美国]? Fanny:No,no.It lives ________[在] Africa and Asia. Jackie:Can it ________[飞]? Fanny:I’m sorry it can’t. Jackie:Is it big? Fanny:Yes,it’s very big and ________[重的]. Jackie:What ________[颜色] is it?Is it white or ________[黑色]? Fanny:It’s white. Jackie:Oh,I see.It’s ________[大象]. 二、找出不同类的单词。（10′） （）1 A.sofa B.table C.check （）2 A.noodle https://www.doczj.com/doc/bc934721.html,k C.way （）3 A.fish B.wolf C.lion （）4 A.bike B.car C.write （）5 A.tree B.farm C.grass （）6 A.big B.small C.other ( ）7 A.eat B.listen C.brown
《剑桥小学英语Join In ——Book 3 下学期》教材教法分析2012-03-12 18:50:43| 分类：JOIN IN 教案| 标签：|字号大中小订阅. 一、学情分析： 作为毕业班的学生，六年级的孩子在英语学习上具有非常显著的特点： 1、因为教材的编排体系和课时不足，某些知识学生已遗忘，知识回生的现象很突出。 2、有的学生因受学习习惯及学习能力的制约，有些知识掌握较差，学生学习个体的差异性，学习情况参差不齐、两级分化的情况明显，对英语感兴趣的孩子很喜欢英语，不喜欢英语的孩子很难学进去了。 3、六年级的孩子已经进入青春前期，他们跟三、四、五年级的孩子相比已经有了很大的不同。他们自尊心强，好胜心强，集体荣誉感也强，有自己的评判标准和思想，对知识的学习趋于理性化，更有自主学习的欲望和探索的要求。 六年级学生在英语学习上的两极分化已经给教师的教学带来很大的挑战，在教学中教师要注意引导学生调整学习方式： 1、注重培养学生自主学习的态度 如何抓住学习课堂上的学习注意力，吸引他们的视线，保持他们高涨的学习激情，注重过程的趣味化和学习内容的简易化。 2、给予学生独立思考的空间。 3、鼓励学生坚持课前预习、课后复习的好习惯。 六年级教材中的单词、句子量比较多，难点也比较多，学生课前回家预习，不懂的地方查英汉词典或者其它资料，上课可以达到事半功倍的效果，课后复习也可以很好的消化课堂上的内容。 4、注意培养学生合作学习的习惯。 5、重在培养学生探究的能力：学习内容以问题的方式呈现、留给学生更多的发展空间。 二、教材分析： （一）.教材特点： 1．以学生为主体，全面提高学生的素质。
小学简单英语自我介绍范文（精选3篇） 小学简单英语自我介绍范文 当换了一个新环境后，我们难以避免地要作出自我介绍，自我介绍可以满足我们渴望得到尊重的心理。但是自我介绍有什么要求呢？下面是收集整理的小学简单英语自我介绍范文，仅供参考，希望能够帮助到大家。 小学简单英语自我介绍1 Good afternoon, teachers! I`m very happy to introduce myself here. I`m Scott. My Chinese name is SunZijing. I`m 13. I`m from Class1 Grade 6 of TongPu No.2 Primary School. I have many hobbies, such as playing ping-pong, playing badminton, listening to music, reading magazines and so on. My favourite food is chicken. It`s tasty and yummy. So I`m very strong. I`m a naughty boy. I always play tricks. And I just like staying in my room and reading books. But I have a dream, I want to be a car-designer. Because I`m a car fan.This is me. Please remember SunZijing! Thank you very much! 小学简单英语自我介绍2 Goodafternoon, teachers! Today, I`m very happy to make a speech here. Now, let me introduce myself. My name is ZhuRuijie.
五 年 级 英 语 测 试 卷 学校 班级 姓名 听力部分（共20分） 一、Listen and colour . 听数字，涂颜色。（5分） 二、 Listen and tick . 听录音，在相应的格子里打“√”。 （6分） 三、Listen and number.听录音，标序号。（9分） pig fox lion cow snake duck
sheep 笔试部分（共80分） 一、Write the questions.将完整的句子写在下面的横线上。(10分) got it Has eyes on a farm it live sheep a it other animals eat it it Is 二、Look and choose.看看它们是谁，将字母填入括号内。(8分) A. B. C. D.
E. F. G. H. ( ) pig ( ) fox ( ) sheep ( ) cat ( ) snake ( ) lion ( ) mouse ( ) elephant 三、Look at the pictures and write the questions.看图片，根据答语写出相应的问题。(10分) No,it doesn’t. Yes,it is.
Yes,it does. Yes,it has. Yes,it does. 四、Choose the right answer.选择正确的答案。(18分) 1、it live on a farm？ 2. it fly？
3. it a cow？ 4. it eat chicken？ 5. you swim？ 6. you all right？ 五、Fill in the numbers.对话排序。(6分) Goodbye. Two apples , please. 45P , please. Thank you.
小学生英语自我介绍演讲稿带翻译 篇一：小学英语自我介绍演讲稿 Good morning everyone! Today I am very happy to make a speech（演讲） here. Now, let me introduce myself. My name is Chen Qiuxiang. I am from Dingcheng center Primary School. I live in our school from Monday to Friday. At school, I study Chinese, Math, English, Music, Computer, and so on. I like all of them. I am a monitor, so I often help my teacher take care of my class. I think I am a good help. And I like Monday best because we have English, music, computer and on Tuesdays. There are four seasons in a year , but my favourite season is summer. Because I can wear my beautiful dress . When I am at home, I often help my mother do some housework. For example, wash clothes , clean the bedroom, do the dishes and so on . and my mother says I am a good help, too. In my spare time, I have many hobbies. I like reading books , going hiking, flying kites .But I like singing best, and my favourite English song is “The more we get
2011-2012 学年度上学期六年级复习题（Unit2-Unit3 ） 一、听力部分 1、听录音排序 ( ) () ()() () 2、听录音，找出与你所听到的单词属同一类的单词 （） 1. A. spaceman B. pond C . tiger （） 2. A.mascots B. potato C . jeans （） 3. A. door B. behind C . golden （） 4. A. sometimes B. shop C . prince （） 5. A. chair B. who C . sell 3、听录音，将下面人物与他的梦连线 Sarah Tim Juliet Jenny Peter 4、听短文，请在属于Mr. Brown的物品下面打√ ( ) ( ) ( ) ( ) ( ) ( ) ( ) 5、听问句选答句 （） 1. A. Yes, I am B. Yes, I have C . Yes, you do （） 2. A.Pink B. A friendship band C . Yes. （） 3. A. OK B. Bye-bye. C . Thanks, too. （） 4. A. Monday. B. Some juice. C . Kitty. （） 5. A. I ’ve got a shookbag. B. I ’m a student. C . It has got a round face. 6、听短文，选择正确答案 （） 1. Where is Xiaoqing from? She is from . A.Hebei B. Hubei C . Hunan （） 2. She goes to school at . A.7:00 B.7:30 C . 7:15 （） 3. How many classes in the afternoon? classes. A. four B. three C . two （） 4. Where is Xiaoqing at twelve o ’clock? She is . A. at home B. at school C .in the park （） 5. What does she do from seven to half past eight? She . A.watches TV B. reads the book C. does homework
Starter Unit Good to see you again知识总结 一. 短语 1. dance with me 和我一起跳舞 2. sing with me 和我一起唱歌 3. clap your hands 拍拍你的手 4. jump up high 高高跳起 5.shake your arms and your legs晃晃你的胳膊和腿 6. bend your knees 弯曲你的膝盖 7. touch your toes 触摸你的脚趾8. stand nose to nose鼻子贴鼻子站 二. 句子 1. ---Good morning. 早上好。 ---Good morning, Mr Li. 早上好，李老师。 2. ---Good afternoon. 下午好。 ---Good afternoon, Mr Brown. 下午好，布朗先生。 3. ---Good evening，Lisa. 晚上好,丽莎。 ---Good evening, Bob. 晚上好，鲍勃。 4. ---Good night. 晚安。 ----Good night. 晚安。 5. ---What’s your name? 你叫什么名字？ ---I’m Bob./ My name is Bob. 我叫鲍勃。 6. ---Open the window, please. 请打开窗户。 ---Yes ,Miss. 好的，老师。 7. ---What colour is it? 它是什么颜色？ 它是蓝红白混合的。 ---It’s blue, red and white. 皮特的桌子上是什么？ 8. ---What’s on Pit’s table? ---A schoolbag, an eraser and two books. 一个书包，一个橡皮和两本书。 9. ---What time is it? 几点钟？ 两点钟。 ---It’s two. 10.---What’s this? 这是什么？ ---My guitar. 我的吉他。
小学生英语自我介绍12篇 Hellow，everyone，my name is XX，I e fromXX，now I will tell you something about myself。 I study at XX school my school is very large ，there are at least 1000students in it。I like all my subjects ，such as Chinese，Maths，English and so on。I like Chinese best between these subjects，I think it is very interesting and amazing。this is me，do you know me now? if you want to know me more，please let me know as soon as possible。 Introducing yourself is very important when you meet new people。You always want to make a good impression when telling others about yourself。Allow me to introduce myself。 My name is XX and I'm from XX 。Right now，I'm a student。I study very hard every day。I like going to school because I'm eager to learn。I enjoy learning English。It's my favorite class。I like to make friends and I get along with everyone。This is the introduction I give whenever I meet new people。It tells people a little bit about me and about what I like to do。 小学生英语自我介绍（二十二）： Hello，my name is_______。I am_______ years old。Now I am studying in_______PrimarySchool。I am in Grade _______，Class_______。 I live in_______。There are _______ members in my family—
外研社剑桥小学英语Join_in四年级上册整体课时教案Starter Unit Let's begin 第一学时: The pupils learn to understand: How are you today? I’m fine/OK. Goodbye. The pupils learn to use: What’s your name? I’m (Alice). How are you? I’m fine. I’m OK. Activities and skills: Decoding meaning from teacher input. Using phrases for interaction in class. Greeting each other. I Introduce oneself. Asking someone’s mane. Teaching process: Step 1: Warm—up. Sing a song. Hello, what’s your name? Step 2: Presentation. 1. What’s your name? I’m…. (1) The teacher introduces herself, saying: Hello, /Good morning, I’m Miss Sun. (2) Asks a volunteer’s name:
What’s your name? The teacher prompt the pupil by whispering, I’m (Alice). (3) Asks all the pupils the same question and help those who need it by whispering I’m…. 2. How are you today? I’m fine. I’m OK. (1) The teacher explains the meaning of How are you today? (2) Tell the class to ask the question all together and introduce two answers, I’m (not very) fine/I’m Ok. (3) Asks all the pupils the same question and make sure that all the students can reply. Step3: Speak English in class. 1. Tells the pupils to open their books at page3, look at the four photographs, and listen to the tape. 2. Asks the pupils to dramatise the situations depicted in the four photographs. A volunteer will play the part of the parts of the other pupils, answering as a group. 第二学时: The pupils learn to use these new words: Sandwich, hamburger, hot dog, puller, cowboy, jeans, cinema, walkman, snack bar, Taxi, clown, superstar.
Join in三年级上册知识点 1.见面打招呼 Hello! = Hi! 你好 Good morning! 早上好！ Good afternoon! 下午好！ Good evening! 晚上好！ (注意：Good night的意思是“晚安”) 2.询问身体健康状况 How are you? 你好吗？ I’m fine. = I’m OK.我很好。 3.临走分别 Goodbye. = Bye bye. 再见。 See you tomorrow. 明天见。 4.Miss小姐Mr先生 5.询问名字 -What’s your name? 你叫什么名字？ -I’m Toby. = My name is Toby. = Toby.我叫托比。 6.Let’s+动词原形 如Let’s go! 我们走吧！ Let’s begin! 我们开始吧！ 7. Are you ready? 你准备好了吗？ I’m ready. 我准备好了。 8.十二个动词 look看listen听mime比划着表达speak讲read读write写draw画colour涂sing唱think想guess猜play玩9.询问物体 -What’s this? 这是什么？ -It’s my dog. / It’s a dog. / My dog. 这是我的狗。 10.my/your+名词 如my apple我的苹果 your apple你的苹果 11.数字0-10 zero零one一two二three三four四five五six六seven七eight八nine九ten十12.询问电话号码 -What’s your phone number? 你的电话号码是多少？ -It’s . / . 13.guess sth 猜东西 如Guess the number. 猜数字 14. What’s in the box? 盒子里有什么？ 15.询问数量 -How many? 多少？ -Nine. 九个。 16. Here is / are sth. 这是……
小学生英语自我介绍范文（9篇） 如今英语交流越来越普遍了，英语版的自我介绍也很普遍，那 么你知道如何写好英语自我介绍吗？下面是收集的小学生英语自我 介绍范文，欢迎阅读借鉴。更多资讯自我介绍栏目。 Good afternoon, teachers! My name is YangXiaodan. I`m 11 now. I`m from Class2 Grade 5 of TongPu No.2 Primary School. My English teacher is Miss Sun. She`s quiet and kind. She`s short and young. My good friend is ZhangBingbing. She`s 12. She`s tall and pretty. We`re in the same class. We both like English very much. I like painting , listening to music, playing puter games and reading books. My favourite food is chicken. It`s tasty and yummy. I often do my homework and read books on Saturdays. This is me. Please remember YangXiaodan. Thank you very much! Gooda fternoon, teachers! My name is XuLulu. I`m 11. I e from Class1 Grade 5 of TongPu No.2 Primary School. There are 4 people in my family. My father is tall. My mother is pretty.My sister has a long hair. And I`m a good student. However, my home is near the school, I often get up early. Because I must work hard. after school, I like playing puter games and reading books. I`d like to eat apples. They are sweet and healthy. And I like
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