ultra-high energy cosmic rays: challenges and opportunities renxin xu ( 徐仁新 ) school of...

Ultra-high Energy Cosmic Rays: Challenges and Opportunities

Renxin Xu (徐仁新 )School of Physics, Peking University

Talk presented at the Conference of

基于羊八井平台的交叉学科研究April 6, 2004, CCAST

“UHECRs” http://vega.bac.pku.edu.cn/rxxu R.X. Xu

SUMMARYSUMMARY Introduction: CRs as HEP FrontierIntroduction: CRs as HEP Frontier UHECRs beyond the GZK cutoffUHECRs beyond the GZK cutoff UHECRs I: beyond standard lore?UHECRs I: beyond standard lore?

Lorentz Invariance Lorentz Invariance TDs: fossils of the GU eraTDs: fossils of the GU era Z-burstsZ-bursts OthersOthers

UHECRs II: UHECRs II: or strangelets? or strangelets? ConclusionsConclusions


Introduction: CRs as HEP FrontierIntroduction: CRs as HEP Frontier


The higher the particle energy attained, the smaller __the scale of physics which can be probed.Cosmic rays vs. Particle physics

1937 (Anderson & Neddermeyer): 1947(Power): 1947(Rochester & Butler): strange part. 0, K, ...

Cosmic rays vs. AstrophysicsGenerally, astrophysics studies “cosmic rays”Astrophysics offers extreme environments

Introduction: CRs as HEP FrontierIntroduction: CRs as HEP Frontier


UHECRs:>~1019eV

The highest!

Within the Galaxy

UHECRs beyond the GZK cutoffUHECRs beyond the GZK cutoff


GZK cutoff: estimations

Ep ~ 1019 eV, ~ Ep/1GeV ~ 1010

ECB ~ 3 K ~ 10-4 eV

Electron rest frameE’CB ~ ECB ~ MeV

Greisen PRL (1966); Zatsepin & Kuzmin JETP (1966)



GZK cutoff: in theoryLoss length

for Proton

with pair

and photopion

productions

Scale of the Galaxy

The GZK cutoff'p p s

196 10 eVthE

with threshold

Other particles

Photon, Iron





No clear GZK cutoff observed Stecker 2003



Prediction vs. observationStecker 2003

UHECRs I: beyond standard lore?UHECRs I: beyond standard lore?


Lorentz symmetry (invariance)Essence of special

relativity:no absolute reference frame

•Poincare group = T(4) + O(1, 3)•Lorentz group O(1, 3) = 3R + 3R´

light propagates at a maximum constant speed c in all reference

12 2 4 2 2 2 2cE m c c p m p

boosts



Mcl ~ l ~ /(Mc)

Quantum space-time foam

Heisenberg relation

Schwartzschild radius Rs~ GM/c2

Virtual particles contribute to curvature significantly when Rs~ l

Plank mass:

Mpl = ( c/G)1/2 = 2.1810-5 g = 1.221016 TeV



Lorentz violation?

(Jacobson, T., Liberati, S. & Mattingly, D. Nature 424, 1019–1021, 2003)

Photons:

Electrons:

32 2 2

pl

( )p

E p m pM

32 2

pl

( )k

k kM

opposites

for L or R

Modified dispersion relations?



LV of UHECRs?Coleman and Glashow (1999, PRD59, 116008):show that only a very tiny amountof LI symmetry breaking is requiredto avoid the GZK effect by suppressingphotomeson interactions betweenultrahigh energy protons and the CBR.



TD: fossils of the GU eraTopological defects (TD) may be produced at the post-inflation stage of the early Universe: e.g., monopoles, cosmic strings, monopoles connected by strings, etc.

Superheavy particles (called X-particles) could be emitted during TD evolution; e.g., annihilation of monopole-antimonopole.

X-particles could be:superheavy Higgs particles

gauge bosons

massive SUSY particles



TD: fossils of the GU era

Fragmentation of X-particles



TD: fossils of the GU era

Berezinsky et al.

PRD58

103515

(1998)



Z-burstsWeakly interacting particles such as neutrinos will have no difficulty in propagating over extragalactic distances

Difficulty in the neutrino hypothesis: The fly’s Eye event occurred high in the atmosphere, whereas the expected event rate for early development of neutrino-induced air shower is down from that of an electromagnetic or hadronic interaction by six orders of magnitude.

But



Z-bursts Weiler, T. 1999, Astropart. Phys., 11 303

Larger cross section of resonant Z0 production by - occurs for

E = mz2/(2m) ~ 41021/(m /eV) eV

[mz ~ 91 GeV, m~ (0.05-8.4) eV; ~10-32cm2]

Clustering of the 1.9 K cosmic background neutrinos

~70% of interactions Z-burst: photons (~30) + nucleons (~2.7)

These photons and nucleons produced within our supergalactic halo propagate to earth and initiate super-GZK air showers



Others

Ultraheavy dark matter particles:

‘wimpzillas’

Other new particles:

e.g., neutral hadrons containing a light

gluino

Black holes in our UniverseBlack holes in our Universe

Supermassive black holesStellar black holesPrimordial black holes

TeV-scale black holes?


Why TeV-scale BHsWhy TeV-scale BHsThe hierarchy problem and EDsThe hierarchy problem and EDs

The Plank scale19

pl / ~ 1.2 10 GeV.M T hc G

But, the electroweak scale

EW ~ TeV.M


Why TeV-scale BHsWhy TeV-scale BHsArkani-Hamed, Dimopoulos & Dvali 1998, Phys. Lett. B429 263

The geometry with Extra spatial

Demensions (EDs) might be responsible

for the hierarchy between Mpl and MEW.

The fundamental gravity scale with n EDs

2 2* pl~ ( )n n nh

M M Rc


What if M* ~ MEW ~ TeV ...Why TeV-scale BHsWhy TeV-scale BHs

Implication I: Large EDs with Radius Rn R (cm)

1 2. 8x10̂ 152 0. 243 1.0x10^-6

4 2.2x10^-9

5 5. 3x10̂ -116 4.5x10^-12

7 7.8x10^-13

Observation?


Why TeV-scale BHsWhy TeV-scale BHsImplication II: TeV-scale mini black holes


The interaction of UHE with ...The interaction of UHE with ...When the c.m. energy Ecm=(2c2mqE)1/2 > M*,

A TeV-scale black hole forms, with an interaction cross section BH ~ rs

2

E

UHE

.Quarkrs


The interaction of UHE with ...The interaction of UHE with ...Gravity interaction dominates if E> ~1015eV

Feng-ShaperePRL 88 (2002)021303“UHECRs” http://vega.bac.pku.edu.cn/rxxu R.X. Xu

Increase thecross section!

Economic

ideal: UHE

The interaction of UHE with ...The interaction of UHE with ...The Schwartzchild radius, with n EDs

The Hawking radiation, with n EDs


The interaction of UHE with ...The interaction of UHE with ...UHE bombarding a nucleon:

in relativistic heavy ion collidersin atmospheric detectors

UHE bombarding a Bare SS:Collapse to a stellar black hole?


What is a Bare Strange Star?

o crusted

o bare

The interaction of UHE with ...The interaction of UHE with ...


The interaction of UHE with ...The interaction of UHE with ...Possible evidence for bare strange stars

Drifting subpulses in radio emissionNo atomic spectrum in X-ray emission

Extreme super-Eddington emission in SGRs

Glitch and free-precession of radio pulsars

For reviews, see: Xu (astro-ph/0211563)Xu (astro-ph/0310050)


The interaction of UHE with ...The interaction of UHE with ...Two steps of collapse:

1st:


The interaction of UHE with ...The interaction of UHE with ...2nd:


The interaction of UHE with ...The interaction of UHE with ...BSSs as probe to the flux of UHE

26 1 27 2

1 event~ ~ 10 s cm

10 y(10km)L

Existof BSS

n low energy limit (eV)

2 2.3x10^20

3 5.1x10^23

4 1.3x10^27

5 3.5x10^30

6 1.0x10^34

7 3.2x10^37


ML03

UHECRs: Strangelets?UHECRs: Strangelets?

What is Strangelet?=>A lump of strange matter

Advantages if UHECRs are strangelets:Larger mass Byond GZK cutoff

Higher electricity Easier to accelerate

Not point-like No collapse to BHs


UHECRs: Strangelets?UHECRs: Strangelets?What is the astrophysical origin of strangelets?

in early cosmology?

after supernova exploration!Acceleration in induced electric field ~ 1017/P10eV

strangelets left behind in debris disk

Planets observed around radio pulsars?

Soft -ray Repeater: burst via collision?


“UHECRs: Strangelets?” http://vega.bac.pku.edu.cn/rxxu R.X. Xu

ConclusionsConclusionsThe cosmic ray study at the highest energy __(UHECRs) is again the frontier of Part. Ph.

UHECRs could potentially open a window __to probe new physics beyond the SM

Strangelets may be candidates of UHECRs, __and may even contribute a significant part __of cosmic rays with energy < 1019 eV!

ultra-high energy cosmic rays: challenges and opportunities renxin xu ( 徐仁新 ) school of...

Documents