1. Proton-proton physics in ALICE
Tapan Nayak
For the ALICE Collaboration
Nov 18, 2006
QM06: pp physics in ALICE

2. Rich pp-physics program at unexplored energies:
Motivation
Rich pp-physics program at unexplored energies:
Soft physics (low pT) program
First time: above the cosmic “knee”
Min. bias events, constraints for under-lying event
Multi-parton interactions (high multiplicity pp events)
Interplay of non-perturbative vs. perturbative physics
New x-Bjorken region ( )
Heavy Flavour
mini-jets and jets
Hadronization processes
Fragmentation processes
Collision energy dependence all above
Potential for new physics
2. pp collisions provide basis for understanding heavy-ion collisions p
Nov 18, 2006
QM06: pp physics in ALICE

3. CERN - Large Hadron Collider (LHC)
Low Luminosity (pp)
Low b (Ions)
14TeV
Luminosity (Lmax): 1034 cm-2 sec-1
Lmax for ALICE: 3x1030 cm-2 sec-1 (200 kHz rate limit as TPC drift time is 90msec)
LHC Schedule:
Aug 2007: Collider Closure
Nov 2007: FIRST collisions: 900 GeV
Dec 2007: 2200 GeV(?)
2008: 14TeV at low luminosity (~6x1026 cm-2sec-1)
LOW LUMINOSITY runs are ideal for ALICE
Nov 18, 2006
QM06: pp physics in ALICE

4. EM Calorimeter (future)
ALICE layout
ITS
Low pt tracking
Vertexing
TPC
Tracking, dEdx
TRD
Electron ID
TOF
PID
HMPID
PID high pt
PHOS
g,p0
MUON
m-pairs
PMD
g multiplicity
V0, T0
Trigger + multiplicity
ACORDE
cosmics
FMD
ch multiplicity
EM Calorimeter (future)
Nov 18, 2006
QM06: pp physics in ALICE

5. Unique features of ALICE
Soft (100MeV) to hard (>100GeV) physics
low pT cut-off (~100 MeV):
=> Low magnetic field: T & Low material budget: 7%
excellent tracking and PID
dedicated di-electrons and di-muons
high resolution calorimeter for direct photons
(charged particles)
Central Barrel (-0.9 < h < 0.9)
tracking, PID (ITS, TPC, TRD, TOF)
single arm RICH
single arm EM cal (PHOS)
Multiplicity
charged (barrel+FMD): (-5.4 < h < 3)
photons in PMD (-2.3 < h < -3.7)
Forward muon arm (2.4 < h < 4.0)
absorber, dipole magnet
tracking and trigger chambers
Trigger, timing, luminosity:
ZDC, V0, T0, CRT
EM Calorimeter (future)
Nov 18, 2006
QM06: pp physics in ALICE

6. AliEn + LCG ROOT Offline Framework AliRoot 1. Event Generators
2. Simulation G3 G4
FLUKA
3. Reconstruction
Virtual MC
ISAJET
AliEn + LCG
AliRoot
AliReconstruction
HIJING
AliSimulation
EVGEN
MEVSIM
Physics Data Challenge (2006)
100M pp events being produced using GRID
10M already produced
Configuration:
min. bias events with Pythia
addition of special physics events
Most of the Analysis framework exists
STEER
PYTHIA6
PDF
PMD
EMCAL
TRD
ITS
PHOS
TOF
ZDC
RICH
HBTP
STRUCT
CRT
START
FMD
MUON
TPC
RALICE
ESD
4. Analysis
HBTAN
Analysis
JETAN
ROOT
Nov 18, 2006
QM06: pp physics in ALICE

7. Detector Performance Momentum Resolution DpT/pT (%) pT (GeV/c) pp
central Pb–Pb pp
DpT/pT (%)
pT (GeV/c)
For pT < 2GeV: %
For 2 < pT < 100GeV: 1-5%
Nov 18, 2006
QM06: pp physics in ALICE

8. Particle Identification3s 2s
Stable hadrons (p, K, p):
100MeV<p<5 GeV (few 10GeV)
Topological identification (K0, K+, K-, L): up to ~ 10 GeV
Leptons (e, m), photons, p0, h:
electrons in TRD: p > 1 GeV,
muons: p > 5 GeV
p0 in PHOS: 1 < p < 80 GeV
Nov 18, 2006
QM06: pp physics in ALICE

9. Pseudo-rapidity distributions
PDC06 data: 400K events (corrections) 100K events (analysis) Different event sample!
Reconstruction with TPC
Reconstruction with SPD
14TeV
Min bias
ALICE h
dN/dh
dN/dh h
UA5, ZPC 33 (1986), CDF, PRD 41 (1990)
All charged
particles
All Charged particles
Good agreement in central region
Nov 18, 2006
QM06: pp physics in ALICE

10. Multiplicity distributions
Multiplicity reaching to >10 times the mean value – interesting for multi-parton interactions, event structure, HBT, multiplicity correlations, rapidity gaps ….
Multiplicity reach
Nch
900GeV
14TeV
5.5TeV
2.2TeV
Probability for an event to have larger than Nch multiplicity
(|h|<0.9)
ALICE
E735: Phys. Lett. B 435 (1998) 453
N/<N1>
546GeV
900GeV
1800GeV <N1>=31
200GeV
<N1>=20
Walker PRD 69 (2004)
Full phase space
Violation of KNO scaling:
Multiplicity distributions expected to “scale” as per to single parton-parton interactions. Deviations attributed to multiparton interactions, jet-minijets.
>80
>60
>40
High multiplicity trigger (threshold on # of SPC chips hit
Nov 18, 2006
QM06: pp physics in ALICE

11. pT distributions ALICE pT (GeV/c) pT reach Charged particles
14TeV
Min bias
ALICE
With 100k events, up to 10 GeV/c
With 100M events, up to 50 GeV/c
pT (GeV/c)
CDF: PRL 61, 1819 (1988)
Charged particles
Nov 18, 2006
QM06: pp physics in ALICE

12. Mean pT vs. Multiplicity
CDF: PRD 65,72005(2002)
Nch
<pT>
Mean pT vs. Multiplicity
ALICE
14TeV
CDF data
pT>0.4GeV/c
All pT
E735 Fermilab
Nch
<pT>
<pT> vs. multiplicity shows different behavior for different identified particles.
In ALICE: inclusive and identified particles will be used in the study with low to high pT range
Protons
Kaons
Pions
Nov 18, 2006
QM06: pp physics in ALICE

13. Strangeness: Baryons, Mesons
Baryon production mechanism
Constraints for underlying events L
reconstruction
(p,p-)
K0s L X W p
Yield per event
0.1
0.01
2X10-4
10-5
0.4
(L+L)/K0s
K0s
14TeV
PYTHIA for min. bias and underlying events (with different settings) give different results.
Flavour dependence of the ratio
Nov 18, 2006
QM06: pp physics in ALICE

14. Baryon # transfer in rapidity
String Junction q
Standard case
This is suppressed
 exp (-1/2 y)
Rossi & Veneziano: gluons carry baryon number resulting in substantial baryon production in central rapidity region. (Kopeliovitch & Zakharov Z. Phys. C43 (1989) 241). Expectation at LHC:
in %
Proton – antiproton asymmetry
H1: Δη ~ 7
– 9.61 ← η
ALICE advantages:
Large rapidity gap
Asymmetry vs. multiplicity
With protons, L, X, W …..
Statistics:
108 events (one month):
109 p, 107 p, 106 L,
104 X, 103 W
Nov 18, 2006
QM06: pp physics in ALICE

15. Heavy flavour in pp Motivation: small xBJ physics ALICE advantages:
pQCD in a new energy domain
HQ fragmentation functions
gluon shadowing
quarkonia production mechanism, charm and beauty cross sections
ALICE advantages:
combination of electronic, muonic and hadronic channels:
Central barrel (-0.9<h<0.9) and Muon arm (2.5<h<4)
coverage close to pT~0 for quarkonia and open charm
high precision vertexing
Physics analysis:
hadronic decays: D0K p, D+-Kpp, DsK K*, Dsfp, …
Leptonic decays:
B l (e or m) + anything.
Inv. mass of lepton pairs: BB, DD, J/Y, Y’,  family, B J/Y + anything.
BB  mmm (J/Y m)
e-m correlations.
W+-  l+- n, Z0l+l-.
J/y polarization
Nov 18, 2006
QM06: pp physics in ALICE

16. d0 pp @ 14TeV D0 Kp (ct = 124mm) Pb+Pb at 5.5TeV B  e + X e B
109 events
14TeV
up to 11–14 GeV/c with 70M evts
D0 Kp (ct = 124mm)
Pb+Pb at 5.5TeV
B  e + X
Primary
Vertex B e X d0
rec. track
Nov 18, 2006
QM06: pp physics in ALICE

17. Quarkonia e+e- Minv m+m- Minv Electronic channel Muonic channel
Statistics: in one year of data (109 min bias events):
8.5x106 J/Y and 6.5x103 U in the muonic chanel
5x105 J/Y in the electronic channel
Nov 18, 2006
QM06: pp physics in ALICE

18. Parton distribution functions Fragmentation function
High pT and jets in pp
Parton distribution functions
Hard scattering c.s.
Fragmentation function
Motivation:
test of perturbative QCD predictions
Jet fragmentation properties
understanding the hadronization processes
Jet rates:
pT>100GeV:
Physics analysis:
Jet trigger (for >100GeV)
high pT spectra
Jet reconstruction & jet structure observables:
jT , fragmentation function, jet-shape
di-hadron correlations
g-Jet correlations
hadrons
leading particle a b c d
Nov 18, 2006
QM06: pp physics in ALICE

19. 2-Jet in pp
Displays for pT
threshold
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Nov 18, 2006
QM06: pp physics in ALICE

20. Direct photons in pp Motivation: thermal photon spectrum
QCD tests, PDF determination
pp: initial stages
Physics analysis:
thermal photon identification
prompt photons: isolation method
photon HBT
Photon tagged jets (g-jet correl.)
Eg = Ejet (g energy provides independent measure of jet energy)
emitted in opposite direction
PHOS R
Dominant processes (pQCD contributions)
g + q → γ + q (Compton)
q + q → γ + g (Annihilation)
ALICE can measure photon tagged jets with
Eg > 20 GeV (PHOS + TPC)
Eg > 40 GeV (EMCAL+TPC)
Nov 18, 2006
QM06: pp physics in ALICE

21. Summary ALICE advantages at LHC:
Low pT, excellent PID & vertex; and reconstruction of high pT jets
Ideal to study min. bias & underlying events at low luminosity
Unique physics with one year data:
Global event characteristics: (inclusive and identified)
h distributions
multiplicity distributions, fluctuations/correlations
pT distributions
Particle ratios, strangeness
Baryon transport, rapidity gap
<pT> vs. multiplicity
Heavy quarks (total c and b cross sections)
high pT spectra, jets
direct photons
………
pp study provides important benchmark for all heavy-ions topics
ALICE pp program is complementary to dedicated pp LHC
Nov 18, 2006
QM06: pp physics in ALICE

22. TPC sector test: Cosmic rays
Single event display
of one pp event
TPC sector test:
Cosmic rays
Nov 18, 2006
QM06: pp physics in ALICE

23. The ALICE Collaboration
Thanks to many of the colleagues who
have helped to put the talk together
- ALICE Physics working groups
and in particular to
ALICE First Physics working group,
Main references:
ALICE PPR – Vol-1
2. ALICE PPR – Vol-2
Nov 18, 2006
QM06: pp physics in ALICE

24. Luminosity & cross sections
Luminosity is related to the rate & cross section:
L in pp measured by: V0, T0, ITS and Luminometers
Reduction in luminosity at ALICE IP from LHC max: 1034
Final L from theoretical c.s. and TOTEM measurements
Expected uncertainty in estimated L : ~5%
Total cross section
Compilation by R.M. Godbole et al.
5.0
5.9 71 77 13 26
103 14
4.3
4.9 55 60
9.5 19 89
5.5
3.5 4 41 45
7.6 15 75
2.2 3
3.4 32 35
6.3
12.5 66
0.9
dN/dh (h=0) (inel)
dN/dh (h=0) (ND)
<Nch> (inel)
<Nch> (ND)
s (SD)
s (el)
s (total)
Sqrt(S) TeV
QGSM model predictions: A.B. Kaidalov
Nov 18, 2006
QM06: pp physics in ALICE

25. LHC Beam Parameters Beam Energy (TeV) 0.45 1.2 6 to 7
Number of bunches 43
156
b* [m] 10
Crossing Angle [mrad]
Transverse emittance [mm]
3.75
Bunch spacing [ns]
2025
525
Bunch Intensity
1x1010
4x1010
Luminosity [cm–2 s–1]
4x1027
1x1028
6x1028
1x1030
3.5x1030
Inelastic Rate [Hz]
144
450
3600
57600
201600
Nov 18, 2006
QM06: pp physics in ALICE

26. Nov 18, 2006
QM06: pp physics in ALICE

27. LHC
B factories
Tevatron
Nov 18, 2006
QM06: pp physics in ALICE

28. J/ψ
108
106
104
102
100
Q2 (GeV2)
100 GeV
Nov 18, 2006
QM06: pp physics in ALICE