Energy Loss in Deconfined Matter. 24. Februar 2013 TUD Julius Gronefeld 1

Transcription

1 Energy Loss in Deconfined Matter 24. Februar 2013 UD Julius Gronefeld 1

2 Structure A brief glimpse at theory Jets and jet quenching Heavy flavor quarks Summary 24. Februar 2013 UD Julius Gronefeld 2

3 Introduction In heavy ion collisions a state of de confined matter is believed to be created often refered to as Quark-Gluon-Plasma. Interesting discoveries already made: Eliptic Flow Measurement of shear viscosity RHIC (pp,auau, dau) s NN = 200GeV. LHC (pp, PbPb, ppb) s NN = 7eV. 24. Februar 2013 UD Julius Gronefeld 3

4 Introduction initial collision thermalization expansion and cooling hadronisation chemical freeze-out kinetic freeze-out 24. Februar 2013 UD Julius Gronefeld 4

5 Forms of Energy loss pqcd based description weakly coupled medium. Collisional energy loss: Energy loss through elastic collisions. Dominant at low p. E = σρl E 1scatt L Radiative energy loss: Inelastic collisions with medium. Dominant at high p. Bethe Heitler Regime: L λ Landau-Pomeranchuk-Migdal Regime: L λ In both regimes: E rad L 2. E E X 8medium9 E-Δ E Δ E agrams for collisional 8lef ArXiv: E-Δ E Δ E 24. Februar 2013 UD Julius Gronefeld 5

6 Forms of Energy loss pqcd based description weakly coupled medium. Collisional energy loss: Energy loss through elastic collisions. Dominant at low p. E = σρl E 1scatt L Radiative energy loss: Inelastic collisions with medium. Dominant at high p. Bethe Heitler Regime: L λ Landau-Pomeranchuk-Migdal Regime: L λ In both regimes: E rad L 2. < E> (GeV) total radiative collisional E i (GeV) ArXiv: Februar 2013 UD Julius Gronefeld 5

7 Forms of Energy Loss Most models model energy loss via radiativ and scattering processes: i.e. Armesto-Salgado-Wiedemann (ASW), Arnold-Moore-Yaffe (AMY), higher twist (H). In case of a strongly coupled medium it could be described via a AdS/CF correspondence. E rad 4 L 3 AdS/CF has sucsess in describing η/s Often used in hybrid models. 24. Februar 2013 UD Julius Gronefeld 6

8 Dead Cone Effect Q Gluon bremsstrahlung of heavy quarks differ from massless partons. Emission of gluons is suppressed at angle smaller than θ 0 = M E Heavy quarks emit less gluons less energy loss. 24. Februar 2013 UD Julius Gronefeld 7

9 Experiments Centrality is an important parameter of a collision. High centrality large number of participants. Pseudorabidity: η = 1 2 ln ( p+p z p p z ) = ln ( tan θ 2 ) Probability % 40-50% 30-40% 20-30% 10-20% 5-10% 0-5% Alice-Data ArXiv: Februar 2013 UD Julius Gronefeld 8 Multiplicity

10 he Nuclear Modification Factor: R AA R AA is a comparison of nucleus nucleus (AA) collisions to proton proton (pp) collisions 1 dn R AA (p ) = AA /dp N coll dn pp /dp If a supression occurs: R AA 1 Scaling factor N coll needs to be determined by theory. 24. Februar 2013 UD Julius Gronefeld 9

11 R AA II R AA normobuncertainty y ny yu R AA y 7un8uh ALICE 6un7uh PbnPbl s NN =2o76beV 5un6uh chargedbparticleslb η <uo8 R AA shows a clear centrality dependence. R AA has a distinct form ny yu 4un5uh 3un4uh 2un3uh Strong suppression at 6GeV/c R AA y less suppression towards high p ny yu yun2uh u 2u 4u p ggevmcd ArXiv: nyuh u 2u 4u p ggevmcd un5h u 2u 4u p ggevmcd 24. Februar 2013 UD Julius Gronefeld 10

12 Jets I Jets are direct probe of energy loss in medium. he energy lost manifests itself in the shape of the jet. ArXiv: Februar 2013 UD Julius Gronefeld 11

13 Jets II Jet suppression I Jets appear to be supressed in RHIC and LHC data. I Supression of about a factor of 2. I Supression has only a weak jet p dependence. 24. Februar 2013 UD Julius Gronefeld 12

14 Jets II Jet suppression Jets appear to be supressed in RHIC and LHC data. Supression of about a factor of 2. Supression has only a weak jet p dependence. CMS (preliminary) PbPb s NN = 2.76 ev ArXiv: Februar 2013 UD Julius Gronefeld 12

15 Jets III Angular Distribution No deflection seen / Nice back-to-back jets No centrality dependence Same results from LHC and RHIC ArXiv: Februar 2013 UD Julius Gronefeld 13

16 Jets IV Jet broadening Jet shapes are influenced by medium. Comparison of jet size in pp and in AuAu collisions. High p jets have simelar width in both collision types. Low p jets are broader. Awayside5Gaussian5Width 1 0&9 0&8 0&7 0&6 0&5 0&4 0&3 0&2 0&1 jet AuAu%50v20r%5205<5p <5405GeVgc pp v25l5detector5uncert& trigger5jet5uncert& Width5including5divjet5smearing& SAR5preliminary Energy is distributed to soft hadrons assoc p <GeVgcj ArXiv: Februar 2013 UD Julius Gronefeld 14

17 Heavy Flavour Hadrons Heavy flavour quarks are produced in hard scattering processes. Experience whole history of the medium. Gluons interact stronger with medium than quarks & dead-cone-effect Hadrons that originate from heavy quarks are less suppressed than hadrons formed by gluon. R π AA < Rcharm AA < R B AA 24. Februar 2013 UD Julius Gronefeld 15

18 Heavy Flavour Hadrons D & π R AA measured for D and π-mesons D-mesons (containing one charm) might be less suppressed than π s For high p : R D AA Rπ AA R AA h if8 if6 if4 ifh i wf8 wf6 wf4 wfh PbdPbl s NN =<hf76<ev w o to Average<D ld ld l< y <wf5l<wd7f5v with<pp<p dextrapolated<reference Charged<particlesl< η <wf8l<wdiwv Charged<pionsl< η <wf8l<wdiwv w w 5 iw i5 hw h5 Cw C5 4w p ggevncx LI DER ArXiv: Februar 2013 UD Julius Gronefeld 16

19 Heavy Flavour Hadrons In peripheral collisions: RAA B Rcharm AA R N ch AA In central region: R N ch AA < Rcharm AA < RAA B Measurement consistent with expectation BU: Different y & p -Range R AA J/ψ BP)6-5<p <30)GeV/cP) y <1-2)hCMSP)prel-= J/ψP)6-5<p <30)GeV/cP) y <1-2)hCMSP)prel-= DP)6<p N ch 6<p <12)GeV/cP) y <0-5)hALICE= <12)GeV/cP) y <0-8)hALICE= PbbPb s NN =2-76)eV N part ArXiv: Februar 2013 UD Julius Gronefeld 17

20 heory vs. Experiments R AA dvo h * 5* Average=D +=D +=D += y <hvs Charged=particles+= η <hvb Wide range of models. Most describe tendency correctly. AdS/CF over predicts the suppression. d hvb hvf hvh hvo PbDPb+ ALICE hdohp=centrality s NN = ov MF= ev d Vitev=rad= I< Vitev=rad=*=dissoc= I< WHDG=rad=*=coll= II< AdSgCF=Drag= III< Langevin=HLo= IV< Coll=*=LPM=rad= V< BAMPS= VI< CUJEdvh= VII< BDMPSDASW=rad= VIII< h h o H F B dh do dh df p GeVgc< t ALI PUB ArXiv: o H F B dh do dh df p GeVgc< t 24. Februar 2013 UD Julius Gronefeld 18

21 heory vs. Experiments All parameters are scaled to the density, which is assumed to scale with charged particle multiplicity. WHDG is a LO-calculation. 24. Februar 2013 UD Julius Gronefeld 19 b) ArXiv:

22 Summary Energy loss manifests itself in jet suppression and shape. Awayside5Gaussian5Width 1 0&9 0&8 0&7 0&6 0&5 0&4 0&3 0&2 0&1 jet AuAu%50v20r%5205<5p <5405GeVgc pp v25l5detector5uncert& trigger5jet5uncert& Width5including5divjet5smearing& SAR5preliminary assoc p <GeVgcj 24. Februar 2013 UD Julius Gronefeld 20

23 Summary Energy loss manifests itself in jet suppression and shape. Color charge and dead-cone-effect lead to different R AA. R AA J/ψ BP)6-5<p <30)GeV/cP) y <1-2)hCMSP)prel-= J/ψP)6-5<p <30)GeV/cP) y <1-2)hCMSP)prel-= DP)6<p N ch 6<p <12)GeV/cP) y <0-5)hALICE= <12)GeV/cP) y <0-8)hALICE= PbbPb s NN =2-76)eV N part 24. Februar 2013 UD Julius Gronefeld 20

24 Summary Energy loss manifests itself in jet suppression and shape. Color charge and dead-cone-effect lead to different R AA. Modelling energy loss stays a challenging task. 24. Februar 2013 UD Julius Gronefeld 20

25 hank you for your attention 24. Februar 2013 UD Julius Gronefeld 21