1. for the ALICE collaboration University of Tennessee at Knoxville
Results from ALICE
Christine Nattrass
for the ALICE collaboration
University of Tennessee at Knoxville

2. Exploring QCD at high temperatures
Quark-gluon plasma
Deconfined - more degrees of freedom
TC ~ 175 ±8 MeV →εC ~ GeV/fm3
Confined - fewer degrees of freedom
F. Karsch, et al.
Nucl. Phys. B605 (2001) 579
ε/T4~ # degrees of freedom 2

3. The phase transition in the laboratory

4. CMS
LHCb
8.6 km
2.2 km
ATLAS LHCf
ALICE

5. CMS
LHCb
8.6 km
2.2 km
ATLAS LHCf
ALICE

6. ALICE ~1000 members ~30 countries ~100 institutes 6
Oct 2008 Split J. Schukraft

7. Size: 16 x 26 meters
Weight: 10,000 tons
Detectors: 18 7

8. Trigger detectors: When do we have a collision?
Size: 16 x 26 meters
Weight: 10,000 tons
Detectors: 18
Trigger detectors: When do we have a collision? 8

9. Trigger detectors: When do we have a collision?
Size: 16 x 26 meters
Weight: 10,000 tons
Detectors: 18
Trigger detectors: When do we have a collision?
Tracking detectors: Where did the particle go? 9

10. Trigger detectors: When do we have a collision?
Size: 16 x 26 meters
Weight: 10,000 tons
Detectors: 18
Trigger detectors: When do we have a collision?
Tracking detectors: Where did the particle go?
Identification detectors: What kind of particle is it? 10

11. Trigger detectors: When do we have a collision?
Size: 16 x 26 meters
Weight: 10,000 tons
Detectors: 18
Trigger detectors: When do we have a collision?
Tracking detectors: Where did the particle go?
Identification detectors: What kind of particle is it?
Calorimeters: How much energy does the particle have? 11

12. p+p collisions

13. Pb+Pb collisions

14. Bulk properties
Christine Nattrass (UTK), Southeastern Section of the APS, October 21, 2011 14

15. Centrality dependence of dNch/dη
PRL 106, (2011)
RHIC data scaled by 2.1
PHENIX
PRC 71, (2005)
dNch/dη = Number of charged tracks per unit pseudorapidity
η = pseudorapidity
= - ln[tan(θ/2)]

16. Centrality dependence of dNch/dη
RHIC data scaled by 2.1
PRL 106, (2011)
PHENIX
PRC 71, (2005)
dNch/dη = Number of charged tracks per unit pseudorapidity
η = pseudorapidity
= - ln[tan(θ/2)]
Npart = number of participating nucleons

17. Transverse Energy
(GeV)
EThad from charged hadrons directly measured by the tracking detectors
ftotal from MC to convert into total ET
From RHIC to LHC
~2.5 increase dET/dh/ (0.5*Npart)
Energy density (Bjorken)
et ~ 16 GeV/(fm2c) RHIC: et =5.4±0.6 GeV/(fm2c)
PRC71: (2005)
PRC70: (2004)
Centrality dependence similar to RHIC (PHENIX)

18. √sNN dependence dET/dh/(0.5*Npart) ~ 9 in 0-5% dNch/dη/(0.5*Npart) ~ 8
~5% increase of Npart (353 → 383) → 2.7 x RHIC (consistent with 20% increase of <pT>)
dNch/dη/(0.5*Npart) ~ 8
2.1 x RHIC 1.9 x pp (NSD) at 2.36 TeV
growth with √s faster in AA than pp
Grows faster than simple logarithmic scaling extrapolated from lower energy
PRL105, (2010)
PRC71:034908,2005
√sNN = Center of mass energy per nucleon

19. Probes of the Quark Gluon Plasma
Christine Nattrass (UTK), Southeastern Section of the APS, October 21, 2011 19

20. Probes of the Quark Gluon Plasma
Medium
Want a probe which traveled through the collision

21. Probes of the Quark Gluon Plasma
nucleus
Want a probe which traveled through the collision
QGP is short lived → need a probe created in the collision

22. Probes of the Quark Gluon Plasma
nucleus
Want a probe which traveled through the collision
QGP is short lived → need a probe created in the collision We expect the medium to be dense → absorb probe

23. Single particles
Measure spectra of hadrons and compare to those in p+p collisions or peripheral A+A collisions
If high-pT hadrons are suppressed, this is evidence of jet quenching
Assumption: sufficiently high-pT hadrons mostly come from jets
Unmodified spectra:
𝑅 𝐴𝐴 = 1/ 𝑁 𝑒𝑣𝑡 𝐴𝐴 𝑑 2 𝑁 𝑐ℎ 𝐴𝐴 /𝑑η 𝑑𝑝 𝑇 〈 𝑁 𝑐𝑜𝑙𝑙 〉 1/ 𝑁 𝑒𝑣𝑡 𝑝𝑝 𝑑 2 𝑁 𝑐ℎ 𝑝𝑝 /𝑑η 𝑑𝑝 𝑇

24. Nuclear modification factor (RAA)
Unidentified hadrons- π,K,p
𝑅 𝐴𝐴 = 1/ 𝑁 𝑒𝑣𝑡 𝐴𝐴 𝑑 2 𝑁 𝑐ℎ 𝐴𝐴 /𝑑η 𝑑𝑝 𝑇 〈 𝑁 𝑐𝑜𝑙𝑙 〉 1/ 𝑁 𝑒𝑣𝑡 𝑝𝑝 𝑑 2 𝑁 𝑐ℎ 𝑝𝑝 /𝑑η 𝑑𝑝 𝑇

25. Nuclear modification factor (RAA)
𝑅 𝐴𝐴 = 1/ 𝑁 𝑒𝑣𝑡 𝐴𝐴 𝑑 2 𝑁 𝑐ℎ 𝐴𝐴 /𝑑η 𝑑𝑝 𝑇 〈 𝑁 𝑐𝑜𝑙𝑙 〉 1/ 𝑁 𝑒𝑣𝑡 𝑝𝑝 𝑑 2 𝑁 𝑐ℎ 𝑝𝑝 /𝑑η 𝑑𝑝 𝑇

26. Nuclear modification factor (RAA)
K0S K±
~1116 MeV/c2
~494 MeV/c2
~140 MeV/c2
K0S π+ π-
~8.6 cm
𝑅 𝐴𝐴 = 1/ 𝑁 𝑒𝑣𝑡 𝐴𝐴 𝑑 2 𝑁 𝑐ℎ 𝐴𝐴 /𝑑η 𝑑𝑝 𝑇 〈 𝑁 𝑐𝑜𝑙𝑙 〉 1/ 𝑁 𝑒𝑣𝑡 𝑝𝑝 𝑑 2 𝑁 𝑐ℎ 𝑝𝑝 /𝑑η 𝑑𝑝 𝑇

27. Baryon anomaly: Λ/K0S

28. Baryon anomaly: Λ/K0S Recombination
Ann.Rev.Nucl.Part.Sci.58: ,2008

29. Charm nuclear modification factor
D meson
~1865 MeV/c2 D0 π+ K-
~123 μm D+ π+ K-
312 μm
𝑅 𝐴𝐴 = 1/ 𝑁 𝑒𝑣𝑡 𝐴𝐴 𝑑 2 𝑁 𝑐ℎ 𝐴𝐴 /𝑑η 𝑑𝑝 𝑇 〈 𝑁 𝑐𝑜𝑙𝑙 〉 1/ 𝑁 𝑒𝑣𝑡 𝑝𝑝 𝑑 2 𝑁 𝑐ℎ 𝑝𝑝 /𝑑η 𝑑𝑝 𝑇

30. Conclusions
Charged particle production and transverse energy follow same trends as seen at RHIC
Energy higher than experimental extrapolation, lower than many models
High pT particle production suppressed to ~0.15 of what we would expect from scaling p+p collisions → hot, dense medium produced
Significant suppression observed even for heavy quarks

31. Backup slides

32. Non-photonic electrons
Beauty + Charm
pQCD
Beauty Electrons pp

33. Charm cross section pp