Recent results in proton-lead collisions with ALICE at the LHC from RUN 2012 and 2013

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1 Recent results in proton-lead collisions with ALICE at the LHC from RUN 2012 and 2013 the APCTP 2013 LHC Physics Workshop at Korea August 6-8, 2013 Konkuk University, Seoul, Korea Toru Sugitate for the ALICE collaboration Hiroshima University ALICE the APCTP LHC Physics Workshop at Konkoku Univ. Korea 6-8 August 2013 T. Sugitate

2 Outline of my Talk 2 Physics goal ALICE setup Physics in p-a Recent results from p-pb pseudo-rapidity density nuclear modification factor baryon to meson ratio, and some related topics Summary

3 Physics Goal 3 WMAP has unique capabilities measuring various particles in wide p T ranges (typ GeV) with excellent PID abilities in extreme particle densities at the LHC, to study Quark-Gluon-Plasma, Understand the properties of strong QCD, and then to reveal the primordial Universe filled with the QGP. What s happened before the afterglow in the primordial Universe? CBM11

4 LHC at CERN 4 s pp = 7 in , 8 in 2012, and 14 TeV in design s Pb-Pb = 2.76 in , and 5.5 TeV in design s p-pb = 5.02 in 2012/13, and 10.0 TeV in design CMS LHCb ALICE ATLAS s NN at LHC = 28 x RHIC =320 x SPS = 1000 x AGS

5 ALICE from pp to A-A at the LHC First pp collision on Nov. 23, 2009 published on EPJ C65: , 2010/Jan pp runs at 0.9, 2.36, 2.76, 7 and 8 TeV in Historical discovery on July 4, 2012, but not yet in ALICE.. New window with p-a p-pb pilot run in Sept p-pb production run at 5.02 TeV for 30 nb-1 in Jan/Feb First Pb-Pb collisions on Nov. 8, Pb-Pb runs at 2.76 TeV/A in First p-pb Collision, September 2012 Yearly LHC HI publication as of July 2013 by ALICE EB HI Total ALICE HI ATLAS HI CMS HI

6 Asymmetric Single-Ring Collider 6 To circulate each beam in same B : + TeV/A s NN = 5.02 TeV and y cm = To synchronize each beam : Pb beam needs around 4mm shorter closed-orbit than proton s at the top energy. Move beam on to off-momentum orbit by adjusting RF frequency by the LHC authority.

7 ALICE Apparatus in 2012/13 7 ZDC (not shown) at ~116m from IP L3 magnet at 0.5T For Run-2 starting 2014, various consolidation/ upgrade in progress ; complete TRD install new DCAL install 4 th PHOS DAQ rate-up HMPID EMC TPC TOF ITS Detector : Size: 16 x 26 meters Weight: 10,000 tons Cap. cost: 158 MCHF Collaboration : 1200 members 131 institutes 36 countries TRD PHOS

8 ALICE PID Performance 8 TPC ITS TOF TRD HMPID Excellent particle identification for various species Particle detection over a wide rapidity range, and p T down to ~0.1GeV/c Low-mass trackers and fine vertex capability Quarkonia detection down to p T =0

9 Physics in p-a 9 Controlled experiment to study the QGP Baseline observables Self-check of pqcd understanding Investigate initial condition Disentangle initial/final state effects Parameterize nuclear PDF at small-x Explore QCD in nuclear medium Study jets in cold nuclear matter Search hints of CGC/Glasma

10 Pseudo-Rapidity Density 10 Charged particle pseudo-rapidity density measured by the tracklet analysis with SPD ( η <2). Phys. Rev. Lett. 110(2013) Applied Non-Single-Diffraction (NSD) event selection. Comparison with models Most models agree within 20%. Saturation models predict a steeper η-dependence than the data observed. The data favors models that incorporate shadowing. p Pb

11 Energy Dependence of Density 11 Charged particle pseudorapidity density in pp, p(d)-a and A-A at mid-rapidity : normalized with the number of participants calculated with the Glauber model. Phys. Rev. Lett. 110(2013) For p-pb at 5.02TeV, the density dn ch /dη = (syst), corresponding to (syst) per <N ch >. The density per <N ch > in p-a is proportional to s NN 0.1.

12 Charged Particle Spectra 12 Transverse momentum distribution of primary charged particles in central rapidities in the min bias (NSD) events, compared with a pp reference. Phys. Rev. Lett. 110(2013) Reconstructed by ITS and TPC ( η <0.8). Systematic uncertainty of % and NSD normalization uncertainty of 3.1%. The transverse momentum spectra exhibit a weak pseudo-rapidity dependence.

13 Nuclear Modification Factor 13 Charged particles in p-pb exhibit a binary scaling (R=1) for p T > 2GeV/c, indicating no visible initial state effects. Phys. Rev. Lett. 110(2013) The strong suppression observed in Pb-Pb, which increases with centrality, could attribute to a formation of hot and dense partonic matter. R AA d N coll 2 N d / dpt d pp N / dp d AA 2 T N coll T AA INEL pp

14 R ppb Comparison with Models 14 Saturation (CGC) models: Consistent with the data Large uncertainties Phys. Rev. Lett. 110(2013) pqcd models with shadowing Consistent with the data Some discrepancies at high p T HIJING 2.1 The model incorporated with shadowing describes dn ch /dη, however, It fails to describe high-p T region. Without shadowing fails at low-p T.

15 Jet Modification Factor 15 Charged jet reconstructed by the anti-k T algorism with R=0.4 in min. bias p-pb collisions. Charged jet spectrum corrected for background from underlying events and for detector effects. No jet suppression observed within the uncertainty. Yield ratio with a different R parameter consistent with a PYTHIA prediction.

16 J/ Modification Factor 16 The ratio R ppb decreases towards forward rapidity. No apparent rapidity dependence in backward region. Uncertainty dominated by the pp reference. Forward/backward ratio free of errors from the pp reference. Comparison with models : Good agreement with models incorporating shadowing (EPS09 NLO) and/or a contribution of coherent parton energy loss. CGC model by Fujii et.al. underestimates data.

17 Various Identified Spectra 17 Transverse momentum distributions with the Blast-Wave fits in several VZERO-A multiplicity classes

18 Lambda/K o s ratios in p-pb vs pp 18 The ratios in p-pb show significant increase at intermediate momenta with increasing VZERO multiplicity. The ratios in p-pb show strong depletion at low-p T region. The data in p-pb shows similar p T dependence as observed in Pb-Pb, but much weaker.

19 Long-range Angular Correlation 19 High multiplicity events Low multiplicity events Phys. Lett. B719(2013)29 A double-ridge structure appears by subtracting the jet-like correlations. Same yields in near and away sides for all p T classes, increasing with the multiplicity. The double ridge structure has not been expected by HIJING. The phenomena under investigation.

20 ALICE RUN-1 and the Future 20 year system energy s NN TeV integrated luminosity 2010 Pb Pb 2.76 ~ 10 mb Pb Pb 2.76 ~ 0.1 nb p-pb/pb-p 5.02 ~ 30 nb -1 RUN2 (2015, 2016, 2017) : will allow to approach the 1 nb -1 for Pb-Pb collisions, with improved detectors and double energy. RUN3 + RUN4 (19, 20, 21 and 24, 25, 26): 10 nb -1 detector improvements. with major So: three phases, each jumping one order of magnitude in statistics and progressively improving the detectors.

21 Summary 21 A rich harvest of physics results has just started in RUN-1. Very interesting results from p-pb collisions have come out. Various models describe the p-pb data, but no single model describes all the aspects. The identified particle spectra are well described with a Blast-Wave model including the radial flow. The ratio R ppb of charged particles at central rapidity is unity, indicating no visible initial effects seen. The ratio R ppb of quarkonia production decreases towards forward rapidity, suggesting finite effects, aka, shadowing and/or coherent parton energy loss and/or something else. The double ridge structure observed in the long-range angular correlation could suggest a hint of new phenomena. RUN-2 starts soon with the LHC full energy, which promises us even richer! We look forward to a great future with you. Stay tuned!

22 ALICE Collaboration Countries 124 Institutes MCHF capital cost History of the ALICE Experiment: Design R&D Construction Installation > Commissioning 4 TP addenda along the way: 1996 Muon spectrometer 1999 TRD 2006 EMCAL 2010 DCAL South Korea Slovak Republic Peru Pakistan Poland Turkey South Africa Russia Romania Thailand Sweden Spain Norway Ukraine UK United States Brazil Armenia ALICE Members (Total: 1199 Members*) CERN China Chile Croatia Cuba Czech Republic Denmark Finland France Germany Netherlands Mexico India Greece Hungary JINR Japan Italy *Alice Collaboration Data Base (ACDB) records, January 2012