0. The charming side of ALICE
Kai Schweda
Physikalisches Institut
University of Heidelberg / GSI Darmstadt
VH-NG 147
24 Oct 2012
PRISMA colloquium, JGU Mainz

1. Building Blocks of Matter
Quantum Chromodynamics (QCD) is the established theory of strongly interacting matter.
Gluons hold quarks together to from hadrons:
Gluons and quarks, or partons, typically exist in a color singlet state: confinement.
meson
baryon
24 Oct 2012
PRISMA colloquium, JGU Mainz

2. PRISMA colloquium, JGU Mainz
Quark Gluon Plasma
Source: Michael Turner, National Geographic (1996)
24 Oct 2012
PRISMA colloquium, JGU Mainz

3. Temperaturen im Universum

4. Collisions of atomic nuclei

5. PRISMA colloquium, JGU Mainz
Time Scales
QGP life time 10 fm/c ≈ 310-23 s
thermalization time 0.2 fm/c ≈ 710-25 s
formation time (e.g. charm quark): 1/2mc = 0.08 fm/c ≈ 310-25 s
collision time 2R/g = fm/c ≈ 210-26 s
Plot: courtesy of R. Stock.
24 Oct 2012
PRISMA colloquium, JGU Mainz

6. PRISMA colloquium, JGU Mainz
Outline
Introduction
LHC and ALICE
Charm-quark production in pp
Charm-quark production in Pb-Pb
Hot results from p + Pb (!)
Summary / Outlook
24 Oct 2012
PRISMA colloquium, JGU Mainz

7. Der Large Hadron Collider am CERN
Alice
LHC TeV c - 10 km/h
Tevatron TeV c km/h
RHIC GeV c km/h
Geiger and Marsden MeV c * 5%

8. Resolution: 600M pixels (750 Mbytes)
Size: 16 x 16 x 25 meters
Resolution: 600M pixels (750 Mbytes)
Readout: 17.5 terabytes/s, ~4 Gbytes/s to tape
TRD
ITS
TPC
Central barrel (ITS, TPC, TRD, TOF) || < 0.9
Muon spectrometer: -4.0 < y < -2.5 8

9. ALICE: >1300 members, 120 institutes, 35 countries
24 Oct 2012

10. s
ALICE in 2004

11. 3 x 2 Layers Silicon Technology
Strips
SSD
Inner Tracking System
~ 10 m2 Si detectors, 6 layers
double sided Strips, Drift, Pixels
Pixels
SPD
Drift
SDD

12. ITS Russian Dolls - Sliding the SSD/SDD over the SPD
TPC
SPD
SSD/SDD 12

13. TPC im Juni ‘06 13

14. Erste Bleikollisionen in ALICE !
ALICE is designed for
Highest multiplicities dN/d up to 6000
Excellent tracking & particle identification down to lowest momentum ~ 100 MeV/c

15. Particle Identification – dE/dx
dE/dx: 5% resolution
Time-of flight, resolution: 120 ps (Pb-Pb) 160 ps (p-p)
TPC dE/dx: separate p from K up to 1.1 GeV
Time of flight: separate K from up to ~ 1.5 GeV
24 Oct 2012
PRISMA colloquium, JGU Mainz

16. PRISMA colloquium, JGU Mainz
Exotica
4 anti-4He candidates
anti-3H observed
(anti-)helium trigger: J. Klein, PhD thesis;
F. Muecke, bachelor thesis, Univ. Heidelberg, in preparation.
24 Oct 2012
PRISMA colloquium, JGU Mainz

17. Heavy - flavor: a unique probe
mc,b » QCD : new scale
mc,b ≈ const., mu,d,s ≠ const.
initial conditions: test pQCD, R, F probe gluon distribution
early partonic stage: diffusion (), drag () flow, jets, correlations probe thermalization
hadronization: chiral symmetry restoration confinement statistical coalescence J/ enhancement / suppression Q2
time
X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker, N. Xu, and P. Zhuang, PLB 647 (2007) 366.
24 Oct 2012
PRISMA colloquium, JGU Mainz

18. Where does all the charm go ?
J/(charmonium) c
D*+ Ds D0 D±
Total charm cross section: open-charmed hadrons, e.g. D0, D+, D*+, c, … and c,b  e() + X
Quarkonia, e.g. J/ carries 1% of total charm
24 Oct 2012
PRISMA colloquium, JGU Mainz

19. Heavy-quark detection
Open-charm reco. in ALICE
D0  K
D+  K
D*  D0 Ds  KK
Under study:
D0  K
c  pK
c  
c  K0S
plot: courtesy of D. Tlusty.
e.g., D0  K- +  , c = 123 m
displaced decay vertex is signature of heavy-quark decay
24 Oct 2012
PRISMA colloquium, JGU Mainz

20. Open-charm spectra from pp @ 7 TeV
ALICE, JHEP 1201 (2012) 128; arXiv: [hep-ex]; D* analysis: Y. Wang, PhD thesis, Univ. Heidelberg, in preparation;
F. Schaefer, bachelor thesis, Univ. Heidelberg, in preparation.
covers spectrum from 1 up to 24 GeV/c
24 Oct 2012
PRISMA colloquium, JGU Mainz

21. Open-charm cross section
ALICE, arXiv: [hep-ex];
J. Wilkinson, bachelor thesis, Univ. Heidelberg (2011);
S. Stiefelmaier, bachelor thesis, Univ. Heidelberg, in preparation.
LHC: First collider measurements at TeV scale
ATLAS & LHCb agree with ALICE
upper band of theory describes experimental data
24 Oct 2012
PRISMA colloquium, JGU Mainz

22. PRISMA colloquium, JGU Mainz
Charm hadronization
Pv: fraction of D-mesons in vector state (V) to all mesons (V+S), Pv = V / (V+S)
World average: Pv = 0.60 ± 0.01
Stat. model, T=164 ± 10 MeV: Pv = 0.58 ± 0.13, agrees with data
HQET predicts Pv = 3/(3+1) = 0.75
ALICE, arXiv: [hep-ex];
J. Wilkinson, bachelor thesis, Univ. Heidelberg (2011);
S. Stiefelmaier, bachelor thesis, Univ. Heidelberg, in preparation.
24 Oct 2012
PRISMA colloquium, JGU Mainz

23. Energy loss in the medium
J.D. Bjorken, PRD 27 (1983) 140.
z = p(h)/pparton
quark-gluon plasma
Fast parton (i.e. charm quark) propagates in the medium
Loses energy due to gluon bremsstrahlung + elastic collisions
Appears as D-meson at lower momentum wrt pp collisions
 probe QGP
24 Oct 2012
PRISMA colloquium, JGU Mainz

24. Nuclear Modification Factor - RAA
define RAA, expect unity in the absence of nuclear effects (for hard processes)
Ncoll = number of binary nucleon-nucleon collisions
at RHIC, suppression of factor ~5
at LHC, suppression of factor ~6
strong medium effects !
24 Oct 2012
PRISMA colloquium, JGU Mainz

25. AdS/CFT correspondence
J.J. Friess et al., arXiv: [hep-th] (2006).
Maldacena conjecture: string theory and conformal QFT mathematically equivalent
heavy-quark energy loss modeled by embedding a string in AdS space
Prediction: strong suppression for charm, small for beauty
24 Oct 2012
PRISMA colloquium, JGU Mainz

26. Charm: Nuclear Modification
In Pb-Pb collisions: Suppresion by factor ~5 when compared to simple binary scaling from pp
Covers 1 – 36 GeV/c
pp reference measured only up to 24 GeV/c + extrapolation
24 Oct 2012
PRISMA colloquium, JGU Mainz

27. Comparison to other hadrons
Mass ordering in RAA? J/ψ  B (upper) D (middle) π (lower)
g,W,Z-bosons: RAA ≈ 1 (!) checks normalization, does not probe the medium
ALICE, arXiv: [nucl-ex],
CMS Z-boson: Phys. Rev. Lett. 106 (2011)
24 Oct 2012
PRISMA colloquium, JGU Mainz

28. PRISMA colloquium, JGU Mainz
Model calculations
Rising RAA solely due to spectrum in pp
Still have to learn from theory about medium properties, i.e. qhat, ehat
Not an initial state effect
PRISMA colloquium, JGU Mainz
24 Oct 2012

29. RAA - model calculations
D mesons charged hadrons
24 Oct 2012
PRISMA colloquium, JGU Mainz

30. Anisotropy Parameter v2
coordinate-space-anisotropy  momentum-space-anisotropy y py x px
Initial/final conditions, EoS, degrees of freedom

31. 2nd Fourier Coefficient – v2
D-meson v2 analysis:
R. Grajcarek, PhD thesis, Univ. Heidelberg, in preparation.
Substantial v2 of charm, comparable to charged hadrons
24 Oct 2012
PRISMA colloquium, JGU Mainz

32. PRISMA colloquium, JGU Mainz
v2 - Model calculations
Models needs to simultaneously describe v2 and R AA
Stringent constraint, gets tougher with more precision/data
24 Oct 2012
PRISMA colloquium, JGU Mainz

33. PRISMA colloquium, JGU Mainz
Next steps
Extract power spectrum of vn, like WMAP*
Compare pp high multiplicity vs Pb+Pb
Mach cone vs medium response for heavy-quarks (well defined probes)
h/s
*WMAP data: The NASA/WMAP Science team;
QGP plot: B. Schenke, S. Jeon, and C. Gale, arXiV:
24 Oct 2012
PRISMA colloquium, JGU Mainz

34. Heavy  quark Correlations
Charm and anti-charm quarks created in pairs and thus correlated
Look for modifications in Pb+Pb collisions
Study transport properties / thermalization
PYTHIA: p + 14 TeV
Heavy-quark production correlated due to QCD processes such as pair creation (backward), gluon splitting (forward), etc.
Expetced for pp
Modified in PbPb --> probe early thermalization
X. Zhu, M. Bleicher, S.L. Huang, K.S., H. Stöcker, N. Xu, and P. Zhuang, PLB 647 (2007) 366.
G. Tsildeakis, H. Appelshäuser, K.S., J. Stachel, NPA 858 (2011) 86; arXiv: [nucl-ex].
24 Oct 2012
PRISMA colloquium, JGU Mainz

35. Heavy  quark Correlations*
CMS trigger: inspected 200 x 109 p+p collisions
BBbar, establish correlations exist in p+p !
Look out for modifications in Pb+Pb
Heavy-quark production correlated due to QCD processes such as pair creation (backward), gluon splitting (forward), etc.
Expetced for pp
Modified in PbPb --> probe early thermalization
*CMS collaboration:JHEP 1102 (2011) 136; arXiv: v2 [hep-ex].
24 Oct 2012
PRISMA colloquium, JGU Mainz

36. Upgrading the Inner Detector
upgrade Concept recently approved by the ALICE Collaboration
targeted for LHC shutdown
Conceptual Design Report CERN-LHCC
24 Oct 2012
PRISMA colloquium, JGU Mainz

37. LHC: Tentative Schedule
2010/11: long run with pp collisions at 7 TeV
1 month of Pb+Pb collisions each year
2012: long run with pp at 8 TeV
2013: p+Pb control measurement
2013/14: Machine consolidation and training
2014: pp and Pb+Pb at full energy
2017/18: long shutdown, luminosity + detector upgrades
2019: pp and Pb+Pb at high luminosity
24 Oct 2012
PRISMA colloquium, JGU Mainz

38. PRISMA colloquium, JGU Mainz
First glance at p+Pb
ALICE, arXiv: [nucl-ex]; submitted to Phys. Rev. Lett.
ALICE, arXiv: [nucl-ex]; submitted to Phys. Rev. Lett.
24 Oct 2012
PRISMA colloquium, JGU Mainz

39. ALICE - Jetzt geht’s los !
24 Oct 2012
PRISMA colloquium, JGU Mainz