Angular Correlations of Hadrons Measured at the LHC

Transcription

1 Angular Correlaions of Hadrons Measured a he LHC Renconres du Vienam Froniers of QCD: From Puzzles o Discoveries December 5-, Qui Nhon, Vienam Raimond Snellings Urech Universiy --

2 Angular Correlaions ALAS-CONF--74 -% -5% -% -% C( ) N mixed N same d N same /d d d N mixed /d d % 3-4% 4-5% 5-6% Conribuions o he wo-paricle ΔΦ,Δη angular correlaion 6-7% 7-8% 8-9% come from anisoropic flow, jes, resonances, ALAS Preliminary < p - Ld = 8 µb a, p b < 3 GeV HB, ec see also CMS HIN--6

3 Angular Correlaions.4..8 ALAS % C( φ, η) For very peripheral collisions or -3% when riggered wih a high-p paricle he dominan conribuion o he. wo paricle angular correlaions is due o je-correlaions More cenral heavy-ion - collisions look very very differen! 3 anisoropic flow % p , p - 3 η a Pb-Pb.76 ev. ALAS.. 6-8, -% zoomed o < C( φ) < % % φ [rad] ALAS % % -5% % 7-8% 8-9%

4 Anisoropic Flow vn G. Qin, H. Peersen, S. Bass, and B. Muller 6 4 y(fm) y z 4 x, b x(fm) N dn d =+ X n=,4,6,... v n cos n( R) N dn d =+ X n= v n cos n( n) iniial spaial geomery no a smooh almond even-by-even (for which all odd harmonics and sin n(φ-ψr) are zero due o symmery) may give rise o higher odd harmonics and symmery planes in momenum space (deailed probes of iniial condiions) 4

5 measure anisoropic flow hv n i = hhe in( n) ii since he common symmery planes canno be measured even-by-even, we measure quaniies which do no depend on heir orienaion: wo and muli-paricle azimuhal correlaions hhe in( ) ii = hhe in( n ( n)) ii = hhe in( n) ihe in( n) ii = hvni assuming ha only correlaions wih he symmery planes are presen - no always a very good assumpion (conribuions from jes, resonances, ec) 5

6 ALAS. Angular Correlaions % C(Δ φ ) Ld = 8 µb -5% < Δη <5 a b.5 < p,p <. GeV ALAS Preliminary Δ φ vp n,n P v, v n,n n=-6 (full FCal EP n=-6) + v v n,n (FCal P(N) EP n=-6) + v P, P, C(Δ φ ) ALAS-CONF Ld = 8 µb ALAS Preliminary Δ φ. < p -5% < Δ η <5 a,p b < 3. GeV Figure 6: Measured correlaion funcion daa compar paricle correlaion and v 6 measured from EP meho laions. wo paricle azimuhal correlaions can be described efficienly wih he firs 6 vn coefficiens 6 3

7 Can we isolae he flow? if nonflow is negligible flow facorizes hhe in( ) ii = hhe in( n ( n)) ii = hhe in( n) ihe in( n) ii = h ni es wih paricles separaed in rapidiy es wih paricles separaed in p flow is a collecive effec muli-paricle correlaions Lee-Yang Zeroes, cumulans, q-vecors, ec 7

8 does i facorize? V Δ n = Pb-Pb.76 ev -% ALICE arxiv:9.5 V Δ fi ] - [ V nδ Cenraliy < p a.5 < p -% <.5 GeV/c < GeV/c n ] - [ V nδ p, p a [GeV/c] Cenraliy < p 4-5% -3% -% -% -% <.5 GeV/c n a.5 < p < GeV/c C(Δφ) raio Pb-Pb.76 ev, -% cenral < p <.5 GeV/c a.5 < p < GeV/c.8 < Δη <.8 4 Δφ [rad] χ /ndf = 33.3 / 35 4 Δφ [rad] yes i does (o a large exen for more cenral collisions) how large is he flow where facorizaion breaks? o quanify ha one needs oher echniques (muli-paricle) 8

9 muli-paricle correlaions for deecors wih uniform accepance he nd and 4 h order cumulan are given by: Borghini, Dihn and Olliraul, PRC 64, 549 () we go rid of wo paricle nonflow correlaions! we can remove nonflow order by order 9

10 v from cumulans Mehod used : A.Bilandzic, R.Snellings, S. Voloshin, Phys.Rev. C83 () 4493 > ) Δη ( * b Q a Q QC{6} 5-3 ALICE Preliminary, Pb-Pb evens a charged hadrons =.76 ev cenraliy percenile QC{4} QC{8} cenraliy percenile QC{} = {} QC{4} = v 4 {4} QC{6} =4v 6 {6} QC{8} = 33v 8 {8} cenraliy percenile cenraliy percenile cumulans show behavior as expeced when correlaions are dominaed by collecive flow

11 v from muli-paricle correlaions..5 ALICE Preliminary, Pb-Pb evens a =.76 ev (charged hadrons) {} ( Δη > ) {} ( Δη > ) {4} {6} {8} cenraliy percenile behavior as expeced when correlaions are dominaed by collecive flow (difference beween and muli-paricle esimaes mainly due o e-by-e flucuaions in he flow / (EP).6 CMS Preliminary PbPb =.76 ev <p <3., η <.8 {EP} {} {4} {LYZ} Cenraliy (%) CMS PAS HIN-- Figure 8: op panel: Inegraed as a funcion of cenraliy a mid-rapidiy h <.8 for four mehods. Boom panel: Comparisons of resuls: he values from hree of he meh are divided by he resuls from he even plane mehod. he error bars show he sais uncerainies only.

12 he Perfec Liquid K. Aamod e al. (ALICE Collaboraion) PRL 5, 53 () ALICE SAR PHOBOS PHENIX NA49 CERES E877 EOS E895 FOPI 4 (GeV) ( Mid-Cenral ) CMS Preliminary Sa. Errors Only (GeV) CMS (LYZ) ALICE SAR PHENIX PHOBOS CERES NA49 sd NA49 cumul AGS (E877) 3 CMS PAS HIN-- he flow increases abou 3%. he sysem produced a he LHC behaves as a very low viscosiy fluid, consrains dependence of η/s versus emperaure

13 v as funcion of p K. Aamod e al. (ALICE Collaboraion) PRL 5, 53 () {4} % -3% 3-4% -% (SAR) -3% (SAR) 3-4% (SAR) p (GeV/c) G. Aad e al. (ALAS Collaboraion) arxiv: 8.68 ().3 ALAS h ± Pb+Pb =.76 ev 4-5%.. ± ALICE h ± SAR h PHENIX π Pb+Pb Au+Au Au+Au =.76 ev 4-5% = GeV 4-6% = GeV 4-5% 5 5 p [GeV] Ellipic flow as funcion of ransverse momenum does no change much from RHIC o LHC energies, can we undersand ha? CMS PAS HIN-- Figure.35 6: vs. p a < inhe4 5%cenraliyinerval,comparedopreviousex imenal daa: CMS ALICE Pb-Pb {}[7] =.76eV for inclusive charged paricles, PHENIX [] for iden,andsardaaonv.3 PHENIX Au-Au {} for s inclusive charged paricles for-5% he 4 6% CMS inerval [9] NN =GeV (EP Mehod) Sa. Errors Only 5-% CMS.5 CMS Preliminary -5% CMS 5-% CMS 5-6% CMS (GeV/c) 3 Figure 6: Comparison of using he even6 plane mehod as a funcion of p p -5% PHENIX 5-% PHENIX -5% PHENIX 5-% PHENIX 5-6% PHENIX

14 v for idenified paricles Hydro: Shen, Heinz, Huovinen & Song, arxiv: Hydro predicion for Pb-Pb evens a CGC iniial condiions, /s=. K p RHIC hydro LHC hydro =.76 ev, Heinz&Shen K ALICE preliminary, Pb-Pb evens a (PHENIX daa: Au-Au@ GeV) (PHENIX) p (PHENIX) ±, v K ±, v p, v {, >} {, >} {, >} RHIC hydro LHC hydro (CGC iniial condiions) ( /s=.) =.76 ev..5.5 cenraliy %-4% he mass spliing increased compared o RHIC energies (GeV/c) pion and kaon v are described raher well wih hydrodynamic predicions for proons hadronic conribuion imporan p cenraliy %-4% ALICE preliminary, Pb-Pb evens a cenraliy 4%-5% ±, v {, >} ± K, v {, >} p, v {, >} hydro LHC (CGC iniial condiions) ( /s=.) p =.76 ev p (GeV/c) (GeV/c)

15 he Perfec Liquid? in calculaions he RHIC v resuls are close o he ideal hydrodynamical limi. hese calculaions place an upper limi on η/s which is smaller han ~ 4 x AdS/CF bound Based on R. Lacey e al., PRL 98 (7) 93 5

16 Shear Viscosiy η/s = η/s > u3 u u u > u > u3 shear viscosiy will make hem equal and desroy he ellipic flow v higher harmonics represen smaller differences which ge desroyed more easily, and which, if measurable, makes hem more sensiive probes o η/s 6

17 Shear Viscosiy Music, Sangyong Jeon τ=.4 fm/c 6 τ=6. fm/c, ideal τ=6. fm/c, η/s= y [fm] -5 3 ε [fm -4 ] y [fm] ε [fm -4 ] y [fm] ε [fm -4 ] x [fm] x [fm] x [fm] iniial condiions ideal hydro η/s= viscous hydro η/s= pions kaons proons η/s=.8 Larger η/s clearly smoohes he disribuions and suppresses.4. η/s=.6 he higher harmonics (e.g. v3) p (GeV/c) Hydro: Alver, Gombeaud, Luzum & Olliraul, Phys. Rev. C8 () 7

18 he vn s he v3 wih respec o he reacion plane deermined in he ZDC and wih he v paricipan plane is consisen wih zero as expeced if v3 is due o flucuaions of he iniial eccenriciy he v3{} is abou wo imes larger han v3{4} which is also consisen wih expecaions based on iniial eccenriciy flucuaions..5 Alver, Gombeaud, Luzum & Olliraul, Phys. Rev. C () Glauber η/s=.8 CGC η/s=.6 ALICE {, Δη > } {, Δη > } v 4 {, Δη > } {4} /ΨRP v 3/Ψ cenraliy percenile ALICE Collaboraion, arxiv: PRL 7 () 33 We observe significan v3 and v4 which compared o v has a differen cenraliy dependence (already srong consrain for η/s) 8

19 he vn s...8 CMS Preliminary PbPb =.76 ev {4} {}.3 < p η <.8 v 4 {3} v 4 {5} v 4 {LYZ} v 6 {LYZ} < 3. GeV/c. ALAS - Ld = 8 µb Preliminary -5% EP from full FCal v 4 v 5 v 6 5-%. v n %. 3-4%. N par CMS PAS HIN--5 { } { } { } { } { }... For mos cenral collisions v3 and v4 become a inermediae p larger han v p [GeV] p [GeV] Figure 4: v n vs p for several cenraliy classes. he shaded bands indic from ables -5. Noe ha he v 6 is only measured for -4%. 9 ALAS-CONF--74

20 Ellipic and riangular Flow v/ε v3/ε ALICE {}/ε {} ALICE {4}/ε {4} MC-KLN / ε (a) ALICE {}/ε 3 {}.3 MC-KLN / ε 3. MC-KLN η/s =. (b) 3 4 Cenraliy (%) v3/ε3 v/ε.4.. ALICE {}/ε {} ALICE {4}/ε {4} MC-Glb. / ε (c) ALICE {}/ε 3 {} MC-Glb. / ε 3. MC-Glb. η/s =.8 (d) 3 4 Cenraliy (%) Qui, Shen and Heinz, arxiv:.333 he cenraliy dependence and magniude are beer described by predicions using MC Glauber wih η/s=.8

21 Flow Analysis Mehods flow analysis mehods have differen sensiiviy o nonflow and flucuaions n{} = n + v + n{4} = n v Borghini, Dihn and Olliraul, PRC 64, 549 () Bilandzic, Snellings and Voloshin, PRC 83, 4493 () n{6} = n n{8} = n v v excellen opporuniy o sudy flow flucuaions and from hese ge a handle on iniial condiions!

22 v versus cenraliy ALICE Preliminary, Pb-Pb evens a =.76 ev ALICE Preliminary, Pb-Pb evens a =.76 ev...5 (charged hadrons) {} ( Δη > ) {} ( Δη > ) {4} {6} {8} cenraliy percenile wo paricle v esimaes depend on Δη Higher order cumulan v esimaes are consisen wihin uncerainies.5 {, > } {, > } {, > } correced {, > } correced {4} cenraliy percenile wo paricle v esimaes are correced for nonflow based on HIJING he esimaed nonflow correcion for Δη > is included in he sysemaic uncerainy

23 v Flucuaions σ v.6.4 ALICE Preliminary, Pb-Pb evens a ((v {} - {4} )/) σ v =.76 ev σ v / or σ ε / ε.8.6 ALICE Preliminary, Pb-Pb evens a =.76 ev ALICE ((v {} - {4} )/(v {} + {4} )) MC-KLN ((ε {} - ε {4} )/(ε {} + ε {4} )) MC-Glauber ((ε {} - ε {4} )/(ε {} + ε {4} )).4.. MC-KLN (.76 ev) σ ε / ε MC-Glauber (64 mb) σ ε / ε cenraliy percenile v n [ v n{} n{4} ] cenraliy percenile v v n n {} vn{4} v n ' n{} + n{4} Flucuaions are significan and for more cenral collisions no in agreemen wih he eccenriciy flucuaions in MC- Glauber and MC-KLN CGC 3

24 Conclusions Anisoropic flow measuremens provided srong consrains on he properies of ho and dense maer produced a RHIC and LHC energies and have led o he new paradigm of he QGP as he so called perfec liquid A he LHC we observe even sronger flow han a RHIC which is expeced for almos perfec fluid behavior he firs measuremens of v3 and higher vn s have recenly been made a RHIC and a he LHC and indicae ha hese flow coefficiens behave as expeced from flucuaions of he iniial spaial eccenriciy (geomery!) and a creaed sysem which has a small η/s provide new srong experimenal consrains on η/s and iniial condiions 4

25 hanks 5

26 v scaling? Hydro: Shen, Heinz, Huovinen & Song, arxiv:5.36 /n q.5..5 Hydro predicion for Pb-Pb evens a cenraliy 4%-5% hydro K hydro p hydro a small (m-m)/nq he scaling in he daa resemble he scaling as observed in hydrodynamics hydro LHC =.76 ev, Heinz&Shen (CGC iniial condiions) ( /s=.) (m -m )/n q (GeV/c) /n q /n q ALICE preliminary, Pb-Pb evens a cenraliy 4%-5% ±, v {, >} ± K, v {, >} p, v {, >} ALICE preliminary, Pb-Pb evens a cenraliy %-% ±, v {, >} ± K, v {, >} p, v {, >} (m -m )/n =.76 ev q (GeV/c) =.76 ev (m -m )/n q (GeV/c)

27 v3(m,p) and he scaling..5. {} ± ± {} K {} p ALICE preliminary, Pb-Pb evens a cenraliy %-% =.76 ev /n q {} ± ± {} K {} p ALICE preliminary, Pb-Pb evens a cenraliy %-% =.76 ev p (GeV/c) (m -m )/n q (GeV/c) he behavior of v3 as funcion of p for pions, kaons and proons shows he same feaures as observed for v (he mass spliing, he crossing of he pions wih proons a inermediae p) 7

28 Geomery and Harmonics v n Au+Au GeV (b = fm) v v 4 v 5 v p G-L Ma and X-N Wang, arxiv:.549v (GeV/c) For cenral collisions a inermediae p he higher harmonics v3 and v4 cross v and become he dominan harmonics Why do hey cross?? For more cenral collisions his occurs already a lower p 8 v n v n..5.5 Cenraliy -5% {} {} v 4 {} v 5 {} Cenraliy -%. (c) {} {} v 4 {} v 5 {} p (b) (GeV/c) ALICE Collaboraion, arxiv: PRL

29 Flow Flucuaions when (-paricle) nonflow is correced for or negligible! in limi of small (no necessarily Gaussian) flucuaions in limi of only (Gaussian) flucuaions n{} = n + n{4} = n v v v n {} = v n {4} = v n n{} + n{4} = n n{} n{4} = v 9

30 Flow Flucuaions Example: inpu v =.5 +/-. (Gausian), M = 5, N = 6 Gaussian flucuaion behave as prediced also for Lee Yang Zeroes and fiing Q disribuion (more on ha laer) 3