А.КурепинИЯИ РАН

Новые результаты и планы исследованийстолкновений релятивистских ядер

ИТЭФ 24 ноября 2011 1

Содержание

1. Некоторые результаты по Pb-Pb столкновениям при 2.76 Тэв/c на нуклон ( ALICE, CMS, ATLAS )2. Энергетическая зависимость рождения барионов

(NA49, NA61, BES )3. Возможности измерения столкновения ядер на LHCb с фиксированными мишенями4. Поиск новых направлений исследования

2

33

'Baryon anomaly': L/K0

4

Baryon/Meson ratio still strongly enhanced x 3 compared to pp at 3 GeV

- Enhancement slightly larger than at RHIC 200 GeV- Maximum shift very little in pT compared to RHIC despite large change in underlying spectra !

Ratio at MaximumRHICL/K0

x 3

Charged Particle RAA

QM2011 J. Schukraft 5

PLB 696 (2011) 30-39

Extrapolated reference=> large syst. error

5

Jet quenching via hadron suppression

Phys. Lett. B 696 (2011) [22 citations]

Ratio =#(particles observed in AA collision per N-N (binary) collision)

#(particles observed per p-p collision)

suppression

1. Strong depletion of high-pT hadrons in A-A collisions– parton energy loss (jet quenching)2. Qualitatively new feature : evolution of RAA as a function of

pT

3. New, much anticipated constraint for parton energy-loss models

Centralcollisions

Cross-section

RAA

1

6

77

Particle production in Pb-Pb:Azimuthal anisotropy

xy z

Initial spatial anisotropy

py

px

Final momentum anisotropy22

22

xy

xy

22

22

2yx

yx

pp

ppv

Reaction plane defined by “soft” (low pT) particles

Elliptic flow

INTERACTIONS( hydrodynamics? )

Reaction plane

xy z

Reaction plane

8

Measure Properties of the Medium Created in Pb+Pb

Collisions

1. Collective behavior observed in Pb-Pb collisions at LHC (+0.3 v2RHIC)

v2(pT) similar to RHIC – almost ideal fluid at LHC ?2. New input to the energy dependence of collective flow3. Additional constraints on Eq-Of-State and transport properties

PRL 105, 252302 (2010) [36 citations]

Most extreme state of matter ever created in the lab …

STAR at RHIC

9

• Precision measurement of h/s:– current RHIC limit: h/S < (2-5) x 1/4p– h/S < 1/4p => conjectured AdS/CFT limit is wrong– h/S > 1/4p => measure s– h/S ≈ 1/4p => quantum corrections

which are O(10-30%) in AdS/CFT!• 20% in v2 ~ 1/4p > need few % precision

•Precision: How ?

– fix initial conditions (geometrical shape is model dependent, eg Glauber, CGC)– quantify flow fluctuations s (influence measured v2, depending on method)– measure non-flow correlations d (eg jets)– improve theory precision (3D hydro, 'hadronic afterburner', ...)– .........

CERN, 2 Dec 2010 J. Schukraft

10 Azimuthal Flow: What next ?

sh mkT2

STAR at RHIC

PRL 105, 252302 (2010)

22

22

}4{

}2{

nnn

nnn

vv

vv

s

ds

10

1111

1212

Flow & 2 Particle Correlations

13

Almost any structure can be described with enough coefficients !- But not if we impose factorization C(pT1, pT2)=v(pT1)*v(pT2) (or take coefficients from flow analysis).

Correlations (|h|>0.8) can be described consistently with 'collective flow' hypothesis for pT < 3-4 GeV ( consistent with 'collectivity ')only partially or not at all for pT > 5 GeV

'away side jet'

2 ) P

≈ coefficients from flow analysis

coefficients from C(PT1,PT2) analysis

14

1515

16

17

RCP

e+e-

J/Y suppression: Compared to..

18

Surprisingly (?) : less suppression than RHIC !RCP(Alice/Atlas): suppression stronger at high pT ??

Caveats:- J/Y (B) ≈ 10% (LHCb) => RAA(prompt) lower by ≈ 0.05- compare to Phenix e+e- ? => less difference, still significant- shadowing(LHC) > shadowing(RHIC) ? => RAA goes up ?- cold nuclear matter suppression ?

Very intriguing, nevertheless ..

Phenix mm

RAA

ATLAS

RCP

shadowing range

?

1919

20

21

22

The HornStatus before 2010

23

The Horn

STAR points from L. Kumar, QM 2011

STAR (BES) results confirm NA49 findings !24

The Horn, LHC point

LHC point follows the established trend

J. Schukraft, QM 2011LHC point from:

25

The Horn

26

No structure in elementary collisions

(too small system for canonical picture)

No structure for negative particles

(different sensitivity to baryon density)

p+p (4π)

27

• step-like pattern is confirmed• no structure in elementary reactions

• similar structure seems to develop

• step-like pattern is confirmed

The StepreReduction of transverse expansion

1m

dNdm

constem tT

28

29

30

31

.

Fixed target charmonium production with proton and lead beams at LHC

A.B.Kurepin, N.S.Topilskaya, M.B.Golubeva INR RAS, Moscow

1. Physics motivation. 2. Geometrical acceptances for J/ measurement at ALICE for PbPb interactions at s= 5.5 TeV and pp interaction at s = 14 TeV. 3. Evaluation of geometrical acceptances for PbPb and p-A fixed target J/ measurement by dimuon spectrometer of ALICE. 5. Luminosity and counting rate estimation. 6. Conclusions.

New Opportunities Workshop…..N.S.Topilskaya, CERN – 13 May 2009.32

.

Colliders (RHIC,LHC)

New Opportunities Workshop….. CERN – 13 May 2009.

AA collisions Pb-Pb 2750 GeV/nucleon, √s = 71.8 GeV

Fixed-target (LHC) – new opportunity – energy between SPS and RHIC

p-A 7000 GeV , √s = 114.6 GeV (5000 GeV, √s = 96.9 GeV)pA collisions

AA collisionsRHIC CuCu, AuAu √s =130 GeV, 200 GeVLHC PbPb √s = 5.5 TeV

pA collisionsRHIC pp, dAu √s =130 GeV, 200 GeVLHC pp, pA √s = 14 (10) TeV

Fixed-target data (SPS, FNAL, HERA)

AA collisionsSU, PbPb, InIn

SPS: NA38, NA50, NA60√s(GeV) 19.4 17.3

pA collisions HERA-B, E866, NA50/51, NA38/3, NA60 √s(GeV) 41.6 38.8 29.1/27.4 19.4 27.4/17.3

33

Fixed target experiment Pb-Pb, T=2750 GeV, s=71.8 GeV.

J/ are generated at z=0 and outside of ITS at z=+50 cm.

J/ are generated using pT-spectra with HERA and PHENIX form, consistent with COM model, but parameters are energy scaled: dN/dpT~pT[1+(35ppT/256 <pT>)2]-6 with <pT>= 1.4, and using y-spectra as Gaussian with mean value ycm=0 and s=1.1

J/ are accepted in the rapidity range -2.5<η<-4.0 (-2.98<η<-4.14), and each of 2 muons in the degree range 1710 <θ<1780 (174.20 <θ< 178.20) for generation J/ at z=0 (z=+50 cm).

z=0 Iacc = 12.0%

z=+50 cm

Iacc = 8.79%

34

Fixed target experiment pA, T=7000 GeV, s=114.6 GeV. J/ are generated at z=0 and outside ITS at z=+50 cm.

J/ are generated using pT-spectra with the same parametrization with energy scaled parameter: dN/dpT~pT[1+(35p pT/256 <pT>)2]-6 where <pT>= 1.6, and using y-spectra as Gaussian with mean value ycm=0 and s=1.25.

z=0

Iacc = 8.54%

z=+50 cm

Iacc = 5.98%

35

Luminocity, cross sections(xF>0) , counting rates

System s snn spA=snnA0.92 BspA L Rate (TeV) (µb) (µb) (%) (µb) (cm-2s-1) (hour-1)

pp 14 32.9 32.9 4.7 0.091 3∙1030 982ppRHIC 0.200 2.7 2.7 3.59 0.0057 2∙1031 410pPbfixed 0.1146 0.65 88.2 5.98 0.310 1.5∙1029(*) 168pPbfixed 0.0718 0.55 74.6 7.97 0.349 1.5∙1029 189pPbNA50 0.0274 0.19 25.8 14.0 0.212 71029(**) 535PbPbfixed 0.0718 0.55 10130 7.97 47.5 3.2∙1027(***) 547

(*) pPbfixed, 500 µ wire, 1012 protons/60 min, z=+50 cm(**) pPbNA50, 3107 protons/s, Eur. Phys. J. C33(2004) 31(***) PbPb cross section, 6.8∙108 ions/60 min 36

Выводы

1. На ионном пучке LHC получены новые результаты о взаимодействии ультрарелятивистских ядер, которые существенно дополняют данные , полученные на коллайдере RHIC

2. Однако конкретных указаний на качественно новые эффекты не обнаружено

3. Необходимо искать новые пути исследования: эксперименты при более низких энергиях расширение набора сталкивающихся ядер , которые вполне достижимы в ближайшее время

3737

38

3939

4040

4141

Study the onset of deconfinement

Onset of Deconfinement:early stage hits transition line,

observed signals: kink, horn, stepT

µB

energy

Kink

Horn

Step

collision energy

hadr

on p

rodu

ctio

n pr

oper

ties

AGS SPS RHIC

42

Particle production in Pb-Pb:Azimuthal anisotropy

xy z

Initial spatial anisotropy

py

px

Final momentum anisotropy22

22

xy

xy

22

22

2yx

yx

pp

ppv

Reaction plane defined by “soft” (low pT) particles

Elliptic flow

INTERACTIONS( hydrodynamics? )

Reaction plane

xy z

Reaction plane

43

Measure Properties of the Medium Created in Pb+Pb

Collisions

1. Collective behavior observed in Pb-Pb collisions at LHC (+0.3 v2RHIC)

v2(pT) similar to RHIC – almost ideal fluid at LHC ?2. New input to the energy dependence of collective flow3. Additional constraints on Eq-Of-State and transport properties

PRL 105, 252302 (2010) [36 citations]

Most extreme state of matter ever created in the lab …

STAR at RHIC

44

Jet quenching via hadron suppression

Phys. Lett. B 696 (2011) [22 citations]

Ratio =#(particles observed in AA collision per N-N (binary) collision)

#(particles observed per p-p collision)

suppression

1. Strong depletion of high-pT hadrons in A-A collisions– parton energy loss (jet quenching)2. Qualitatively new feature : evolution of RAA as a function of

pT

3. New, much anticipated constraint for parton energy-loss models

Centralcollisions

Cross-section

RAA

1

45

Di-hadron Correlations in PbPb

Two-particle correlations - conditional [per-trigger] yields and

At Low-pT :

RidgeHydrodynamics, flowAt High-pT :

Quenching/suppression, broadeningPowerful instrument to study system characteristics, including Jet Quenching (recoil jet suppression)

AzimuthalCorrelation~ 180 deg

Leading particle

46

Модель RELDIS: Relativistic ELectromagnetic DISsociation

• RELDIS опирается на модель фотоядерных реакций (ИЯИ, 1995-2008, А.С.Ильинов, И.А.Пшеничнов)

• Поглощение фотонов ядрами – многостадийный процесс: – поглощение фотона на внутриядерном

нуклоне или на квазидейтонной паре (учитывается свыше 100 каналов при энергиях фотонов несколько ГэВ)

– внутриядерный каскад образовавшихся адронов

– статистический распад возбужденного остаточного ядра – модель SMM: конкуренция испарения нуклонов и кластеров - деление - мультифрагментация

47

Single and mutual EMD with ZDC

SINGLE EMD MUTUAL EMD

ZDC signal: Single EMD + Mutual EMD + Nuclear effectsMutual EMD event selection: ZNC && ZNA + ZDC time selection + (ZEM1<10 || ZEM2<10) estimated from simulations to reject nuclear eventsData: 1n peak resolution consistent with RELDIS calculationRatios: 1n/2n; 1n/3n; 2n/3n are under investigation

1n1380 GeV

2n

48

The Dale

s y2 (hydro) = 8

3cs

2

1- cs4

lnsNN

2mN

, with cs

2 13

Reduction of longitudinal expansion

Petersen, Bleicher, nucl-th/0611001v1

s y2 (p - ) = 8

3cs

2

1- cs4

lnsNN

2mN

No new points from STAR and ALICE (PID at mid–rapidity only)

4949

50

Chiral Magnetic Effect ('strong parity violation')

51

RPY 2cos

B+-

Same charge correlations positiveOpposite charge correlations negativeRHIC ≈ LHCsomewhat unexpected

should decrease with Nch

may decrease with √s

.?

cos

+ -

B

?

RHIC

RHIC

Local Parity Violation in strong magnetic Field ?

52

53

54