CERN · 2012. 6. 18. · QCD-Cosmic-V, Paris, 15/06/12 3/30 David d'Enterria (CERN)...

1/30QCD-Cosmic-V, Paris, 15/06/12 David d'Enterria (CERN)

CERNCERN

““QCD at Cosmic Energies – V”QCD at Cosmic Energies – V”Paris, 15Paris, 15thth June 2012 June 2012

David d'Enterria David d'Enterria

Hadronic collisions at Hadronic collisions at cosmic energies: cosmic energies:

What have we learnt from the LHC ?What have we learnt from the LHC ?


Ultrahigh-energy cosmic raysUltrahigh-energy cosmic rays (UHECRs) (UHECRs)

■ Cosmic-ray flux falls very rapidly with energy (power-law: E-n):

■ Flux has 2 slope changes: "knee" at Elab ~ 10

15 eV: E-2.7 → E-3.1

"ankle" at Elab ~ 1018 eV: E-3.1 → E-2.6

☞ What's the origin of these structures ?

■ Cosmic-rays observed up to energies Elab~10

20 eV (GZK-cutoff):

☞ What are their sources ? What's the acceleration mechanism ?

☞ What is their nature (protons, ions) ?

What can the LHC do to solveWhat can the LHC do to solvethose open questions ?those open questions ?


Ultrahigh-energy cosmic raysUltrahigh-energy cosmic rays via EAS via EAS

■ For Elab >1015 eV flux too low for satellites/balloons (1 CR per m2-year):

■ Indirect measurements using the atmosphere as a “calorimeter”:SatellitesSatellites

ExtendedExtendedAir ShowersAir Showers(EAS)(EAS)

~27 X0~11 int

- UV fluorescence light in air (N*) - Cherenkov-light from e±,± at ground


Ultrahigh-energy cosmic rays & QCDUltrahigh-energy cosmic rays & QCD

■ Above 1015 eV CR energy & id determined via hadronic Monte Carlos:

■ CR+Air collisions: QCD interactions at c.m. energies up to √sGZK~300 TeV

ExtendedExtendedAir ShowersAir Showers(EAS)(EAS)

proton

nucleus

gluonsquarks


UHECR at GZK-cutoffUHECR at GZK-cutoff: protons or Fe-ions ?: protons or Fe-ions ?

■ Shower-max position & fluctuations favour heavier ions above 1019 eV

■ Hadronic MC uncertainties propagate to CR mass.

QGSJET-II,SIBYLL: favour protons

EPOS: favours mixture protons+Fe-ions

Auger: PRL 104 (2010) 091101


■ Diffractive/Elastic scattering is ~40% p-p σtot at the LHC Phenomenologically modeled. Energy extrapolations ±20-30% uncertainty.

High-energy hadronic collisionsHigh-energy hadronic collisions

hard core

- No colour flux - Colourless exchange with vacuum quantum-numbers: |Pomeron = (2-gluons in colour-singlet state) - 1 or 2 protons intact. - 1 or 2 rapidity gaps

(gap)

(gap) (gap)

p p

p

p p

- perturbative parton-parton collisions

~60%

~40%

(gap)

■ Hadrons are extended composite objects: Even at asymptotically large c.m. energies, ~40% of hadronic interactions are not “point-like”:

pQC

DpQ

CD

Reg

ge-G

ribov

Reg

ge-G

ribov


Reggeon-Field-Theory hadronic MCsReggeon-Field-Theory hadronic MCs

■ Soft interactions via Reggeons & Pomerons:

■ Perturbative interactions via “cut (hard) Pomerons” (≅ LO pQCD)■ Semi-hard dynamics built-in: - eikonal (multi)parton ladders (p-A, A-A possible) - gluon saturation (via enhanced |P diags)

■ Non-perturbative ingredients: - string fagmentation (Lund model) - beam-remnants

■ Model parameters:- Tuned with accelerator data.- O(20) much less than in std collider MCs

elastic, diffractive & soft-inelastic scatts. described


Semi-hard dynamics: MPI & saturationSemi-hard dynamics: MPI & saturation

RHIC LHC GZK

p,Fe+

gluon densityat Q~Qs

~1.5GeV2 ~4GeV2 ~10GeV2 10-2 -10-3 10-3.5 -10-6 10-5 -10-8 x(y=0,ymax/2):

Qs2 : N,O

■ p-nucleus at GZK cut-off energies: multiple gluon-gluon interactions at x~10-5-10-8 !


Hadronic MCs tuning with collider dataHadronic MCs tuning with collider data

Current modelstuned here

×105 extrapolation√sGZK~300 TeV


Hadronic MCs tuning with collider dataHadronic MCs tuning with collider data

■ The LHC provides a significant lever-arm in providing constraints for hadronic Monte Carlos for UHECR

Current modelstuned here New LHC

data

×105 extrapolation

×103 extrapolation

√sGZK~300 TeV


CERN Large Hadron Collider (LHC)CERN Large Hadron Collider (LHC)

TOTEM

LHCb

ALICE ATLAS

CMS

LHCf

~8.5 km

Lac Léman

Jura

Moedal

p-p collisions up to p-p collisions up to √√s = 14 TeV, s = 14 TeV, ℒℒ=10=103434 cm cm-2-2ss-1-1, 8 mo/yr, 8 mo/yr pPb,PbPb up to pPb,PbPb up to √√s = 8.8,5.5 TeV, s = 8.8,5.5 TeV, ℒℒ=10=1030,2730,27 cm cm-2-2ss-1-1, 1 mo/yr, 1 mo/yr


LHC experiments:LHC experiments: (p (pTT,,ηη) acceptance) acceptance

■ Particle production at the LHC over ~ 2✕ln(√s)/mp ~ 20■ All phase-space virtually covered (1st time in a collider) !

p-p @ 14 TeVParticle flow

Energy flow

ALI

CE


Cosmic-ray MCs (pre-LHC) vs. LHC dataCosmic-ray MCs (pre-LHC) vs. LHC data

Hadron multiplicity

Forward particle spectra Average transverse momentum

Hadronic cross-sections


Cosmic-ray MCs vs. LHC data (I)Cosmic-ray MCs vs. LHC data (I)

Hadron multiplicity




Total & elastic p-p cross sectionsTotal & elastic p-p cross sections■ Non-computable from QCD Lagrangian (maybe lattice ?), but

constrained by fundamental QM relations: Froisart bound, optical theorem, dispersion relations.

■ LHC p-p x-section predictions:

■ Pre-LHC model uncertainties driven by E710–CDF 2.6σ disagreement

10 %.20+− σtot(LHC) = 90-120 mb

■ p-Air x-sections even more uncertain (Glauber model):

R.Ulrich, eConf C0906083 (2009)


LHC p-p inelastic LHC p-p inelastic cross sectionscross sections■ Visible inel. x-section ATLAS,CMS~60 mb mostly overestimated by MCs:

■ Most models over-/under-estimate high-/low-mass diffraction. ■ Increasingly unbiased evt. selection best reproduced by QGSJET01,-II-4

CMS 7-TeV preliminary PAS-FWD-11-001

TOTEM

CMS


LHC p-p inelastic x-section vs. sqrt(s)LHC p-p inelastic x-section vs. sqrt(s)

■ sqrt(s)-evolution better reproduced by QGSJET01:


LHC p-p tot.LHC p-p tot. . .// el.el. // inel. cross sectionsinel. cross sections

■ TOTEM tot~ 98 mb falls right on top of COMPETE fit prediction (which goes in between E710–CDF at 1.8 TeV ...)

Auger

TOTEM


Cosmic-ray MCs vs. LHC data (II)Cosmic-ray MCs vs. LHC data (II)

Hadron multiplicity




■ Charged-hadron data vs CR models:

Particle pseudorapidity densityParticle pseudorapidity density

0.9 TeV 2.36 TeV 7.0 TeV

■ 900-GeV data well reproduced (MCs tuned to SppS, Tevatron)

■ Particle multiplicity less well predicted at 7.0 TeV

■ Simplest models (QGSJET-01, SIBYLL 2.1) seem to do better than more recent ones ...

[DdE-Engel-Ostapchenko-Pierog-Werner, Astr.Phys. 35 (2011) 98]


■ 0.9, 2.36, 7.0 TeV charged-hadron data vs PYTHIA & PHOJET:

Particle multiplicity not well reproduced at 2.36, 7.0 TeV by most tunings:

Less particles predicted in collider MCs than in real data.

Particle pseudorapidity densityParticle pseudorapidity density

0.9 TeV 2.36 TeV 7.0 TeV

[DdE-Engel-Ostapchenko-Pierog-Werner, Astr.Phys. 35 (2011) 98]


Particle pParticle pseudorapidity density vs. sqrt(s)seudorapidity density vs. sqrt(s)

(NSD) (INEL)

■ Power-law s, ~0.1 controlled by soft-hard pT-cutoff (sat. scale) evolution

■ Very large differences predicted at √sGZK~ 300 TeV ! QGSJET-II (~40) > QGSJET01 (~20) > SIBYLL 2.1,EPOS 1.99 (~8)

■ GZK: models with dNch/d~20 favoured (p-p data at 14-TeV needed)


■ PYTHIA tunes with power-law s, ~0.1 for soft-hard pT-cutoff reproduce best evolution:

■ Large differences predicted by PYTHIA-tunes at √s~300 GeV ! PYTHIA 8.130 (~20) > ATLAS-CSC (~15) > Perugia-0 (discarded)

Particle pParticle pseudorapidity density vs. sqrt(s)seudorapidity density vs. sqrt(s)[DdE-Engel-Ostapchenko-Pierog-Werner, Astr.Phys. 35 (2011) 98]

(NSD) (INEL)


■ Models ~OK with average multiplicity/event, may miss the event-by-event multiplicity probability at low & large Nch :

■ Improvements of diffractive & multiparton interactions needed.

LHC event multiplicity probabilitiesLHC event multiplicity probabilities

2.36 TeV

7.0 TeV

High-multiplicity tailsMultiplicity peaks


Cosmic-ray MCs vs. LHC data (III)Cosmic-ray MCs vs. LHC data (III)

Hadron multiplicity




■ Gluons start to overlap at “saturation scale”

▪ Hadrons ~ “Color Glass Condensate” below Qs ▪ Saturation effects enhanced in nuclei:

~ 6

Average pAverage pTT dominated by saturation dynamics dominated by saturation dynamics

Large # of partons per transverse area

Glu

on d

ensi

ty

pQCD (linear)

CGC

√s

■ Asymptotic pQCD g-g x-section peaks at pT~ Qs(√s)~1-4 GeV


■ is sensitive to pQCD x-sections & gluon-saturation■ should approach asymptotically the saturation scale: ~ Qsat

Average pAverage pTT vs. sqrt(s) vs. sqrt(s)

■ CRs MCs predict very slow increase (but EPOS, due to collective flow)■ At GZK: ~ 0.6 – 1.0 GeV/c (PYTHIA: ~ 0.7 – 1.5 GeV/c)


■ Is also sensitive to final-state “collective” effects ?■ for ,K,p strongly increases with p-p “centrality”:

Average pAverage pTT vs. particle multiplicity vs. particle multiplicity

■ EPOS, including final-state collective flow, reproduces behaviour

■ PYTHIA qualitative reproduces the Increase but it is tune-dependent

PAS-FSQ-12-014 (T. Pierog)


Cosmic-ray MCs vs. LHC data (IV)Cosmic-ray MCs vs. LHC data (IV)

Hadron multiplicity




Forward hadron production: Forward hadron production: || | = 5.2 – 6.6| = 5.2 – 6.6■ Important influence on cosmic-ray EAS development: - multi-parton interactions & beam-remnants tuning

■ Good CMS-data vs. CR-model agreement for energy density.

Neutral mesons (0,,K0s → 's):

■ Collider-MCs do not reproduce well the slope of TOTEM particle density.

arXiv:1205.4105

PAS-FWD-11-003

CASTOR

TOTEM


Very forward hadron production: Very forward hadron production: || | ~ 8. - 11.| ~ 8. - 11.■ Important influence on cosmic-ray EAS development: - leading baryon (inelasticity) & had-to-e.m. energy transfer (0 → )

Neutral mesons (0,,K0s → 's):

■ Mean pT of zero-degree pions is sqrt(s)-independent. EPOS shows the best overall agreement

■ > ±50% data-model differences for zero degree photon showers.

arXiv:1205.4578

PLB703 (2011) 128

LHCf


Summary: CR MCs & LHC dataSummary: CR MCs & LHC data■ Reasonable agreement (all MCs bracket data), though no model reproduces consistently all results:

■ Modeling improvements : diffraction, MPI, saturation (plus parameter retunings) ongoing: EPOS 2.X, QGSJET-II-4■ Coming LHC data will provide more CR MCs constraints: proton-nucleus distributions (p-Pb @ 5 TeV in Nov'12).

■ No significant change of multiparticle production at the LHC (~1016 eV): "CR knee" at ~1015.5 eV not due to new (unobserved) particles.■ Energy evolution of semi-hard QCD dynamics is crucial for predictions (Nch, ) at GZK-cutoff energies (~10

20 eV).


Summary: Impact of QCD@LHC for UHE CRsSummary: Impact of QCD@LHC for UHE CRs

low-x PDFs

parton saturation

σ tot , elastic scatt. diffraction

UE, MPI, MB

beam remnants Reduced uncertainties on UHECR mass & spectrum: p-Fe mixture ?

(pre-LHC)

QGSJET

p

p

(T. Pierog)


Backup slidesBackup slides


proton-Pb proton-Pb @@ √√s = 8.8 TeVs = 8.8 TeV■ Particle (dN/d) & energy (dE/d) rapidity densities:

DdE, R.Engel, T.McCauley, T.Pierog: arXiv:0806.0944 [astro-ph]

[ZDCs/LHCf calorimeter region]

[full ]


UHECRs energy & identificationUHECRs energy & identification

■ Position & fluctuations of shower maximum:

[Blumer-Engel-Horandel, PPNP 68(2009)293]

■ Number of e± & muons:

Depth: > p > AXmax(p)~Xmax(Fe)+150 g/cm

2

Shower-to-shower fluctuations: smaller for ions than proton.

❬ln A❭~ log(Ne/N


Examples of implications for EASExamples of implications for EAS

■ Reduced dN/dη (esp. fwd):

Less penetration: lower Xmax (~ -30 g/cm

2)

■ Reduced charm cross sections:

Less muons

Drescher, Dumitru, StrikmanPRL 94 (2005) 231801

Machado&GoncalvesJHEP0704 (2007) 028


proton-Pb proton-Pb @@ √√s = 8.8 TeVs = 8.8 TeV■ Particle (dN/d) & energy (dE/d) at forward rapidity :

(*) DdE, R.Engel, T.McCauley, T.Pierog: arXiv:0806.0944 [astro-ph]

Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38

Date post:	27-Jan-2021
Category:	Documents
Upload:	others
View:	1 times
Download:	0 times

CERN · 2012. 6. 18. · QCD-Cosmic-V, Paris, 15/06/12 3/30 David d'Enterria (CERN)...

Documents