Quarkonium results:lessons from LHC run-1

E. Scomparin (INFN-Torino)

Trento, March 16-20 2015

Introduction, pre-LHC summary LHC run-1 substantial progress on charmonium/bottomonium studies! Open points and prospects for run-2 Conclusions

A lively topic

2

Quarkonium suppression as a “QGP thermometer”

My own “thermometer” of the interest of the community in quarkonium studies

Number of citations of the seminal Matsui’s and Satz’s paper

09/11/09 1279

06/12/10 1344

22/11/11 1447

09/11/12 1644

17/11/14 2041

14/03/07 1176

Citations doubled in the last ~8 yearsStill a very “hot” topic!

Tc

~30 years of experiments

3

(peripheral) (central)

From the ‘80s…

…until today!

SPS (NA38-NA50-NA60)

RHIC (PHENIX-STAR)

LHC (ALICE-CMS)

C. Baglin et al. (NA38), Phys. Lett. B220(1989) 471

CMS Coll., PRL 109(2011) 222301

HI studies: reference processes

4

Choice of “suitable” reference process for the modification of the quarkonium yields proved to be crucial (and much debated!)

SPS energy Drell-Yan process Cancellation of syst. uncertainties No initial/final state effects in the explored kinematic region Small statistics

RHIC, LHC energy RAA

Limited cancellation of uncertainties Does not account for initial/final state effects not related to the medium Precise reference data can be collected

Ideal reference Normalization to open charm Most “natural” reference initial state effects cancel out Differential comparisons not straightforward

Charm energy loss shifts D-meson pT

J/ suppression removes yield Open charm data have non-negligible uncertainties (especially at low pT)

q

q

+

-

HI studies: role of CNM

5

Considered as a crucial step for the understanding of A-A results However

Description of pA data in terms of various CNM effects is difficult Extrapolation pA AA can be effect-dependent and/or model dependent

At SPS Use of effective quantity abs (break-up cross section) tuned on pA data and then directly extrapolated to A-A (via L-variable)

At RHIC Combination of shadowing (factorized out using nuclear PDFs parameterizations) and break-up Centrality dependence exhibits surprising (understood?) effects

At LHC Break-up cross section negligible (Coherent) energy loss effects become important First attempts (see later) at an extrapolation pA AA

5

p

c

cg

J/, c, ...

6

Low energy results: J/ from SPS & RHICSPS (NA38, NA50, NA60)

sNN = 17 GeV

First evidence of anomalous suppression (i.e. beyond CNM expectations) in Pb-Pb collisions

~30% suppression compatible with (2S) and c decays

RHIC (PHENIX, STAR)sNN = 39, 62.4, 200 GeV

suppression, with strong rapidity dependence, in Au-Au at s= 200 GeV

R.Arnaldi et al.(NA60) NPA830 (2009) 345c A. Adare et al. (PHENIX) PRC84(2011) 054912

7

Low energy results: J/ from SPS & RHICComparison of SPS and RHIC results

Good agreement between SPS and RHIC patterns if cold nuclear matter effects are taken into account

N.Brambilla et al. (QWG) EPJC71 (2011) 1534

Understanding cold nuclear matter effects and feed-downis essential for a quantitative assessment of charmonium physics

Compensation of suppression/recombination effects? Suppression of c and (2S) w/o recombination?

8

Low energy results: (2S) from SPS & RHIC

SPS (NA50) pA, AA @ sNN = 17 GeV RHIC (PHENIX)d-Au @sNN = 200 GeVNA50 Coll., Eur. Phys. J. C 49, 559 (2007)

(2S) is more suppressed than J/ already in pA collisions and the suppression increases in Pb-Pb

PHENIX Coll., PRL 111, 202301 (2013)

unexpected (2S) suppression (forms outside nucleus) stronger than the J/ one in central d-Au

Pb-Pb

p-A

S-U

9

Low energy results: from SPS & RHIC

SPS (NA50) pA, sNN=29 GeV

First measurement at SPS energies. Hint for no strong medium effects on (1S+2S+3S) in pA

RHIC (PHENIX, STAR)dAu, Au-Au sNN = 200 GeV

B. Alessandro (NA50 Coll), PLB 635(2006) 260

RAA compatible with suppression of excited states, with large uncertainties

A. Adare (PHENIX Coll.), 1404.2246L. Adamczyk (STAR Coll.) PLB 735 (2014) 127

Lessons from low-energy A-A…

10

Suppression effect on J/ beyond CNM undisputable at both SPS and RHIC Common interpretation: mainly related to screening/dissociation

in hot (deconfined) matter

Role of J/ regeneration tiny (if any) at SPS energy Quantitatively much debated at RHIC energy

Energy scan very interesting in principle (onset of suppression), but only top energy was explored at the SPS (new NA60+ experiment?) Results at s=39 and 62.4 GeV suffer from large uncertainties (absence of proper reference data)

(2S) largely suppressed in A-A compared to J/ at SPS energy Commonly seen as an effect of its weak binding

resonances out of SPS reach Intriguing results at RHIC, first recent attempt to separate 1S (STAR)

Suppression compatible with complete 2S+3S melting, 1S suppression only for central events

…and questions for LHC

1111

1) Evidence for charmonia (re)combination: now or never!

(3S) b(2P)(2S)

b(1P)

(1S)

2) A detailed study of bottomonium suppression

Do we see enhancement vs centrality ?Do we see J/ flow?Do we see softer pT distributions?

Do we see sequential suppression ?(as recombination does not play a role)

12

The main actors

CMS (high pT)

ALICE (low pT )

CMS Excellent mass resolution for muons(35 MeV for J/) Prompt vs non-prompt Cut low-pT charmonia

ALICE Access mid- and forward-

rapidity (e+e- and + respectively)

Good mass resolution for J/ (~70 MeV for muons, ~30 MeV for electrons)

Full pT acceptance in the whole y-range

Prompt vs non-prompt at y=0

J/ ATLAS CMS

LHCb

ALICEALICE

13

The low pT region: ALICE

B. Abelev et al., ALICEPhys. Lett. B 734 (2014) 314

Centrality dependence of the nuclear modification factor studied at both central and forward rapidities

Inclusive J/ RAA

Small effect of non-prompt contribution

on the inclusive RAA

At forward y, RAA flattens for Npart 100 Central and forward rapidity suppressions compatible within uncertainties

Global syst: 13% e+e- 15% +-

Forward y:No B suppressionRAA

prompt~0.94RAAincl

Full B suppressionRAA

prompt~1.07RAAincl

Central y:No B suppressionRAA

prompt~0.91RAAincl

Full B suppressionRAA

prompt~1.17RAAincl

14

Low pT: comparison ALICE vs PHENIX

Comparison with PHENIX

Stronger centrality dependence at lower energy Systematically larger RAA values for central events in ALICE

Behaviour qualitatively expected in a (re)generation scenario Look at the pT dependence of the suppression

15

Comparison to theory calculations:

Models including a large fraction (> 50% in central collisions) of J/ produced from (re)combination or models with all J/ produced at hadronization provide a reasonable description of ALICE results

Still rather large theory uncertainties: models will benefit from a precise measurement of cc and from cold nuclear matter evaluation

J/ RAA vs centrality: theory comparison

16

A (re)generation “signature”:the pT dependence of RAA

At low pT, for central events, the suppression is up to 4 times larger at PHENIX, compared to ALICE Strong indication for (re)generation

Global syst: 8% ALICE10% PHENIX

17

Moving to higher pT:CMS vs ALICE

Complementary y-coverage: 2.5<y<4 (ALICE) vs 1) 1.6<|y|<2.4 (CMS, left)2) |y|<2.4 (CMS, right)

Qualitative agreement in the common pT range

B. Abelev et al., ALICEPhys. Lett. B 734 (2014) 314

18

CMS results: prompt J/ at high pT

CMS PAS HIN-2012-014CMS-PAS HIN-12-2014

Striking difference with respect to ALICE No saturation of the suppression vs centrality High-pT RHIC results show weaker suppression

No significant pT dependence from 6.5 GeV/c onwards (Re)generation processes expected to be negligible

19

CMS results: prompt J/ at high pT

Striking difference with respect to ALICE No saturation of the suppression vs centrality High-pT RHIC results show weaker suppression

No significant pT dependence from 6.5 GeV/c onwards (Re)generation processes expected to be negligible

CMS PAS HIN-2012-014CMS-PAS HIN-12-2014

20

The contribution of J/ from (re)combination should lead to a significant elliptic flow signal at LHC energy

J/ flow

CMS measures a significant v2 in a region where (re)combination should be negligible due to path-length dependence of J/ suppression

STAR found v2 consistent with 0

ALICE measures v2 (with a significance up to 3 for chosen kinematic/centrality selections) in agreement with transport models including (re)combination

b diffusion

ALICE Coll., Phys. Rev. Lett. 111 (2013) 162301

Moving to p-Pb J/ results: RpPb vs y

21

ALICE and LHCb results in good agreement Strong suppression at forward and mid-y: no suppression at backward y Data are consistent with models including shadowing and/or energy loss Color Glass Condensates (CGC) inspired models underestimate data Dissociation cross section abs<2 mb cannot be excluded

LHCb Coll., JHEP 02 (2014) 072

ALICE Coll., JHEP 02 (2014) 073

RpPb vs pT

22 22

The pT dependence of J/ RpPb has been studied in the three y ranges

backward-y mid-y forward-y

backward-y: negligible pT dependence, RpA compatible with unity mid-y: small pT dependence, RpA compatible with unity for pT>3GeV/c forward-y: strong RpA increase with pT

Comparison with theory: Data consistent with pure shadowing calculations and with coherent

energy loss models (overestimating J/ suppression at low pT, forward-y) CGC calculation overestimate suppression at forward-y

Event activity dependence: QpPb

23 23

/

/

JpppA

JpAJ

pAT

YQ

At forward-y, strong J/ QpA decrease from low to high event activity At backward-y, QpA consistent with unity, event activity dependence

not very significant

CNM effects: from p-Pb to Pb-Pb

24

x-values in Pb-Pb sNN=2.76 TeV, 2.5<ycms<4

x-values in p-Pb sNN=5.02 TeV, 2.03 < ycms < 3.53 210-5 < x < 810-5

x-values in p-Pb sNN=5.02 TeV, -4.46 < ycms < -2.96 110-2 < x < 510-2

Partial compensation between sNN shift and y-shift

If CNM effects are dominated by shadowing RPbPb

CNM = RpPb RPbp = 0.75 ± 0.10 ± 0.12 RPbPb

meas = 0.57 ± 0.01 ± 0.09“compatible” within 1-

210-5 < x < 910-5

110-2 < x < 610-2

Same kind of “agreement” in the energy loss approach

…which does not exclude hotmatter effects which partlycompensate each other

F. Arleo and S. Peigne, arXiv:1407.5054

25

pT-dependence

pA

AAPb-Pb

p-Pb

Pb-Pb

p-Pb

Perform the extrapolation as a function of pT

No more “agreement” between Pb-Pb and CNM extrapolations High-pT suppression is not related to CNM effects At low pT CNM suppression is of the same size of the effects observed in Pb-Pb: recombination ?

Comparing charmonia and open charm: p-Pb

26

ALICE p-Pb results, mid-rapidity, pT integrated

RpPbJ/ = 0.73 0.08 0.15RpPb

D = 0.85 0.05 0.11(weighted average of pT differential points using FONLL cross section (no FONLL unc.)and RpPb(0-1)=RpPb(1-2) )

Assuming RpPb(0-1) = 0.4

RpPbD = 0.82 0.05 0.11

Within uncertainties (and with reasonableextrapolations to pT=0), CNM effects onintegrated J/ and D-mesons production

have the same size

ALICE Coll., PRL 113 (2014) 232301

Comparing charmonia and open charm: p-Pb

ALICE p-Pb results, mid-rapidity, pT differential

Bin-to-bin comparison less straightforward

g

g

D

D

g

g

J/At fixed pT, gluon kinematicscan be (very) different for

single D and J/

ALICE Coll., PRL 113 (2014) 232301

Comparing charmonia and open charm: p-Pb

28

Single muon results available for pT > 2 GeV/c (More) difficult to extract an integrated RpPb

Bin-to-bin comparison not straightforward

p-going direction

Comparing charmonia and open charm: p-Pb

29

Single muon results available for pT > 2 GeV/c (More) difficult to extract an integrated RpPb

Bin-to-bin comparison not straightforward

Pb-going direction

Comparing charmonia and open charm: Pb-Pb

30

RPbPbD = 0.51 0.08 0.09

(weighted average of pT differential points using FONLL cross section (no FONLL unc.)and RpPb(0-1)=RpPb(1-2) )

Assuming RpPb(0-1) = 1

RPbPbD = 0.63 0.08 0.10

RPbPbJ/ = 0.73 ± 0.09 ± 0.06 ± 0.09  

0-10%

Good compatibility (especially assuming RpPb(0-1) = 1) between D and J/ Suppression and regeneration balance Warning: DS, c (not included) may be enhanced in Pb-Pb

ALICE, PLB 734 (2014) 314

Comparing charmonia and open charm: Pb-Pb

31

0-10%

RPbPbJ/ = 0.56 ± 0.02 ± 0.02  ± 0.08  

Forward rapidity: results for muons with pT >4 GeV/c Extrapolation to all pT problematic

ALICE, PLB 734 (2014) 314

J/ in Pb-Pb: run-1 summary

32

Evidence for smaller suppression compared to RHIC Occurrence of recombination is at present the only explanation

pT-dependence of RPbPb also compatible with recombination

Although qualitative interpretation looks unambiguous, the quantitative assessment of the effects at play needs refinement Values for dcc/dy evolved. At present, in the forw.-y ALICE domain:

SHM 0.15 – 0.25 mb (y=4 and y=2.5) – no shadowing Zhao and Rapp 0.5 mb – “empirical” shad. vs no shad. Zhuang et al. 0.4 – 0.5 mb – EKS98 shadowing Ferreiro et al. 0.4 – 0.6 mb + Glauber-Gribov shad. ~ nDSG(min.) > EKS98

LHC run-2 (almost) a factor 2 gain in s would it be possible to extract dcc/dy which gives the best fit to run-1 results, extrapolate to run-2 energy (FONLL?) and give predictions ?

Suppression persists up to the largest investigated pT

Higher pT reach in run-2 increase of RPbPb ? Predictions ?

Interesting indication for azimuthal anisotropies. Run-2 needs Experiment (much) larger statistics Theory solid predictions

J/ in p-Pb: run-1 summary

33

p-Pb data: characterization of CNM effects in terms of shadowing plus coherent energy loss (no break-up) looks satisfactory

Effects are strong, RpPb~ 0.6 at low pT and central to forward rapidity Strong influence of CNM effects in Pb-Pb in the corresponding

kinematic region

Uncertainties on shadowing calculations are large, could one use the LHC data to better constrain shadowing ?

The simple estimate RPbPbCNM=RpPbRPbp (inspired to a shadowing

scenario) leads, once this effect is factorized out, to an even steeper pT-dependence of RPbPb

Also for p-Pb, run-2 energy predictions (s~8 TeV), with parameters TUNED on run-1 results, would allow a crucial test of our understanding of the involved mechanisms

34

The (2S) yield is compared to the J/ one in Pb-Pb and in pp

Improved agreement between ALICE and CMS data (wrt preliminary)

(2S)/J/ in Pb-Pb

CMS (central events)pT>3 GeV/c & 1.6<|y|<2.4 (2S) less suppressed than J/pT>6.5 GeV/c & |y|<1.6 (2S) more suppressed than J/

35

(2S) RpPb vs ycms

Spp

Jpp

JpA

SpAJ

pAS

pA RR2

22

(2S) suppression is

stronger than the J/ one and reaches a factor ~2 wrt pp

Same initial state CNM effects (shadowing and coherent energy loss) expected for both J/ and (2S)

Theoretical predictions in disagreement with (2S) result

Other mechanisms needed to explain (2S) behaviour?

Final state effects related to the (hadronic) medium created in the p-Pb collisions?N.B.: crossing times smaller than formation time, no nuclear break-up (Forward-y: c~10-4 fm/c, backward-y: c~710-2 fm/c)

ALICE Coll., JHEP12(2014)073

36

(2S) QpPb vs event activity The (2S) QpA is evaluated as a function of the event activity

Rather similar (2S) suppression, increasing with Ncoll, for both ALICE and PHENIX results

Spp

Jpp

JpA

SpAJ

pAS

pA QQ2

22

with

QpA instead of RpA due to potential bias from the centrality estimator, which are not related to nuclear effects

Jpp

multpA

JpAJ

pA T

YQ

J/ and (2S) QpPb vs event activity J/ and (2S) QpA are compared vs event activity

forward-y: J/ and (2S) show a similar decreasing pattern vs event activity

backward-y: the J/ and (2S) behaviour is different, with the (2S) significantly more suppressed for largest event activity classes

Another hint for (2S) suppression in the (hadronic) medium?37

(2S): run-1 summary

38

In Pb-Pb collisions the CMS results show an enhancement of the (2S) yield, compared to J/, at intermediate pT, and a suppression at low pT

A convincing explanation of the Pb-Pb results is still lacking

The ALICE preliminary results are marginally compatible with this observation (large uncertainties, low S/B)

In p-Pb collisions a significant suppression, compared to J/, is observed

The effect becomes very strong at backward rapidity, and implies sizeable final-state effects on the (2S)

Formation-time vs crossing-time arguments imply that the suppression may be related to the (hadronic?) medium created in p-Pb collision First theory calculations support this interpretation

Run-2 is expected to yield large luminosity, mandatory for a meaningful study of (2S) in Pb-Pb

39

suppression in Pb-Pb collisions

LHC is the machine for studying bottomonium in AA collisions

Main features of bottomonium production wrt charmonia:

• no B hadron feed-down• gluon shadowing effect

are smaller• (re)combination expected

to be smaller• theoretical predictions

more robust due to the higher mass of b quark

with a drawback…smaller production cross-section

Clear suppression of states in PbPb with respect to pp collisions

CMS Coll., PRL 109, 222301 (2012)

pp

PbPb

40

suppression in Pb-Pb collisions

Strong suppression of (2S)

(1S) suppression compatible with suppression of excited states (50% feed-down)

Sequential suppression of the three states according to their binding energy:

Suppression at LHC is stronger than at RHIC

RAA((1S)) = 0.56 ± 0.08 (stat) ± 0.07 (syst)

RAA((2S)) = 0.12 ± 0.04 (stat) ± 0.02 (syst)

RAA((3S)) <0.1 (at 95% C.L)

CMS Coll., PRL 109, 222301 (2012)

41

Comparison of ALICE vs CMS results

Stronger suppression at forward rapidity than at mid-rapidity, in particular for central collisions

Comparison of ALICE (forward-y) and CMS (mid-y) results

CMS Coll., PRL 109 (2012) 222301 ALICE Coll., PLB 738 (2014) 361

ALICE

CMS

ALICE

CMS

42

Comparison with theory

• Evolving QGP described via a dynamical model including suppression of bottomonium states, but not CNM nor recombination

• 2 different initial temperature y profiles: boost invariant or Gaussian (3 tested shear viscosity)

MO

DEL

The model underestimates the measured (1S) suppression at forward-y, while it is in fair agreement with mid-y data

43

Comparison with theory

• Transport model accounting for both regeneration and suppression

• CNM effects included via an effective absorption cross section (0-2 mb)

MO

DEL

The measured RAA vs centrality is slightly overestimated by the model at forward-y, while it reproduces CMS resultsConstant RAA behavior vs y is not supported by the data

(1S) measured at forward-y by both ALICE and LHCb

Compatible RpA results within uncertainties (but LHCb systematically higher)

Hint for stronger suppression at forward-y (similarly to J/)

Theoretical calculations based on initial state effects seem not to describe simultaneously forward and backward y

44ALICE Coll., PLB 740 (2015) 105-117LHCb Coll., JHEP 07(2014)094

(1S) Production in p-Pb

45

CMS Coll., JHEP 04 (2014) 103 CMS Coll., PRL 109 (2012)

(2S)/(1S) (ALICE)2.03<y<3.53: 0.27±0.08±0.04-4.46<y<-2.96: 0.26±0.09±0.04

Compatible with pp results 0.26±0.08 (ALICE, pp@7TeV)

Initial state effects similar for the three states

p-Pb vs pp @mid-y: final states effects in p-Pb affecting the excited states

p-Pb vs PbPb @mid-y : even stronger suppression of excited states in PbPb

ALICE (and LHCb) observes: CMS analyses the double ratio [(2S)/(1S)]/[(nS)/(1S)]pp

and finds

p-Pb

Pb-Pb

0.83±0.05±0.05

(nS)/(1S) Production in p-Pb

46

(nS)/(1S) vs event activity

Strong decrease with increasing charged particle multiplicity both in pp and p-Pb

production affects multiplicity?

or multiplicity affects the ?

activity around the breaks the state

(1S) produced with more particles than excited states

Weaker dependence when the activity estimator is in a different kinematic region with respect to the

CMS Coll., JHEP 04 (2014) 103

: run-1 summary

47

First detailed study of bottomonia in HI collisions

Suppression of 1S, 2S, 3S states clearly observed More weakly bound states are more suppressed Evidence for sequential suppression

Suppression of 1S state at mid-rapidity consistent with feed-down effects

Rapidity dependence of 1S suppression exhibits surprising features Still not satisfactorily reproduced by models

p-Pb results, still significant uncertainties at forward-y, no sharp conclusions

At central rapidity, evidence for final-state effects on 2S and 3S states

CMS RpPb results still to be delivered

Intriguing features on yields vs event activity

Conclusions (1)

48

LHC run-1 has led to a very significant advance of our understanding of charmonia/bottomonia in hot matter

Charmonium highlight evidence for a new mechanism which enhances the J/ yield, in particular at low pT, with respect to low-energy experiments

In addition Indications for J/ azimuthal anisotropy (non-zero v2) Significant final state effects on (2S) in p-Pb, likely related to the

(hadronic) medium created in the collision

Bottomonium highlight evidence for a stronger suppression of 2S and 3S states compared to 1S. Effect not related to CNM and compatible with sequential suppression of “bottomonium” states

In addition 1S is also suppressed (~50%). Feed-down effect only? y-dependence of 1S suppression to be understood

49

Conclusions (2) Prospects for run-2

Collect a ~1 order of magnitude larger integrated luminosity

High-statistics J/ sample Comparison with run-1 AND with theoretical predictions crucial

to confirm/quantify our understanding in terms of regeneration

Significant (2S) sample Crucial: run-1 results “exploratory” (and interpretation not clear)

High-statistics (1S) sample A significant increase in 1S suppression with respect to run-1 might imply that a high-T QGP is formed (“threshold” scenario)

Differential (2S) and (3S) results from run-1 are limited by statistics Centrality and pT-dependent studies important to assess details of

sequential suppression

Backup

50

51

52

53

RHIC: suppression vs recombination Did we reach a consensus on the role played by recombination at RHIC ?

J/ pT distribution should be softer (<pT

2>) wrt pp

J/ elliptic flow J/ should inherit the heavy quark flow

One should in principleobserve

Evidence not compelling Could weaker suppression at y=0 be due to other effects (CNM, for example)?

CMS, focus on high pT

Muons need to overcome the magnetic field and energy loss in the absorber

Minimum total momentum p~3-5 GeV/c to reach the muon stations

Limits J/ acceptance Midrapidity: pT>6.5 GeV/c Forward rapidity: pT>3 GeV/c

..but not the one (pT > 0 everywhere)

56

Non-zero v2 for J/ at the LHCCMS HIN-2012-001

E.Abbas et al. (ALICE),PRL111(2013) 162301

The contribution of J/ from (re)combination should lead

to a significant elliptic flow signal at LHC energy

A significant v2 signal is observed by BOTH ALICE and CMS The signal remains visible even in the region where the contribution of (re)generation should be negligible Due to path length dependence of energy loss ? Expected for J/ ? In contrast to these observations STAR measures v2=0

Finally, the

57

LHC is really the machine for studying bottomonium in AA collisions (and CMS the best suited experiment to do that!)

First accurate determination of suppression

58

Suppression increases with centrality

First determination of (2S) RAA: already suppressed in peripheral collisions

(1S) (see also ALICE) compatible with only feed-down suppression ?

Probably yes, also taking into account the normalization uncertainty

Compatible with STAR (1S+2S+3S)(but large uncorrelated errors): expected ?Is (1S) dissoc. threshold still beyond LHC reach ? Full energy

(1S) vs y and pT from CMS+ALICE

59

Start to investigate the kinematic dependence of the suppression Suppression concentrated at low pT (opposite than for J/, no recombination here!) Suppression extends to large rapidity (puzzling y-dependence?)

Do not forget CNM…

60

Also in the sector, the influence of CNM is not negligible

With respect to 1S, the 2S and 3S states are more suppressed than in pp… but less than in Pb-Pb confirm Pb-Pb suppression as hot matter effect As a function of event activity, loosely related to centrality in pPb (and surely not in pp!) “smooth” behaviour: to be understood!

RHIC: energy scan

61

System size and energy dependence of RAA

No appreciable dependence on both energy and system size

Not trivial! Requires counterbalancing of suppression+regeneration effects over

a large s-region (note however large global systematics) Warning: CNM effects (shadowing) expected to vary with s

Quarkonia – where are we ?

62

Two main mechanisms at play1) Suppression in a deconfined medium2) Re-generation (for charmonium only!) at high s

can qualitatively explain the main features of the results

ALICE is fully exploiting the physics potential in the charmonium sector (optimal coverage at low pT and reaching 8-10 GeV/c)

RAA weak centrality dependence at all y, larger than at RHIC Less suppression at low pT with respect to high pT

CNM effects non-negligible but cannot explain Pb-Pb observations

CMS is fully exploiting the physics potential in the bottomonium sector (excellent resolution, all pT coverage)

Clear ordering of the suppression of the three states with their binding energy as expected from sequential melting (1S) suppression consistent with excited state suppression (50% feed-down)

Conclusions

63

LHC: first round of observations EXTREMELY fruitful

Many (most) of the heavy-quark/quarkonia related observables were investigated, no showstoppers, first physics extracted

Many (most) of the heavy-quark/quarkonia related observables would benefit from more data to sharpen the conclusions full energy run, 2015-2017 upgrades, 2018 onwards

RHIC: still a main actor, with upgraded detectors

Lower energies: SPS, FAIR

Serious experimental challenge High-B region of the phase diagram unexplored for what concerns heavy quark/quarkonia below 158 GeV/c

From RpAincl to RpA

prompt

64

Assume RpAnon-prompt = 1

The value of RpAprompt can differ significantly from RpA

prompt at large fb

Is the difference significant for ALICE?

65

Exercise

1) Assume RpPbnon-prompt=1

2) Plot RpPbprompt vs fb for the values

of RpPbinclusive measured by ALICE

3) Plot the ALICE point at the fB

value corresponding to the pT

where the measurement is performed

Result

For ALL the pT range accessibleto ALICE, the difference betweenRpPb

inclusive and the calculatedRpPb

prompt is smaller than theuncertainties

PHENIX – new systems/energies

66

Old system (Au-Au) at new energy: still a balancing of suppression and regeneration ? Theory seems to say so….

New system (Cu-Au) at old energy: Cu-going finally different! (probably not a CNM effect) A challenge to theory SPS went the other way round (from S-U to Pb-Pb…)

PHENIX – CNM

67

First study of a charmonium excited state at collider energy

Seems contradicting our previous knowledge

pT dependence of RdAu

Increase vs pT at central/forward y Reminds SPS observation

But different behaviour at backward rapidity Not easy to reproduce in models!

Overall picture still not clear !

STAR -

68

Bottomonium: the “clean” probe 3 states with very different binding energies No complications from recombination

But not that easyat RHIC!

…and this has been split into3 centrality bins…. Compatible with 3S melting

and 2S partial melting

Hints from theory

69

Theory is on the data ! Fair agreement, but…. … one model has no CNM, no regeneration …the other one has both CNM and regeneration (which would be responsible for all (2S) in central events)

Still too early to claim a satisfactory understanding ?

70

(2S) RpPb vs ycms

Can the stronger suppression of the weakly bound (2S) be due to break-up of the fully formed resonance in CNM?

possible if formation time (f ~0.05-0.15fm/c) < crossing time (c)

forward-y: c~10-4 fm/cbackward-y: c~710-2 fm/c

break-up effects excluded at forward-y

at backward-y, since f ~c , break-up in CNM can hardly explain the very strong difference between J/ and (2S) suppressions

Final state effects related to the (hadronic) medium created in the p-Pb collisions?

The (2S) suppression with respect to binary scaled pp yield can be quantified with the nuclear modification factor

zc

L

D. McGlinchey, A. Frawley and R.Vogt, PRC 87,054910 (2013)

arXiv:1405.3796

Charmonia – data samples

71

ALICE Lint (2011) = ~70 b-1 (2.5<y<4), ~28 b-1 (|y|<0.9) Trigger: MB + 2 tracks in the muon trigger chambers (pT> 1 GeV/c)

Background subtraction via like-sign or mixed-event techniques

B. Abelev et al., ALICEarXiv:1311.0214.

Charmonia – data samples

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CMS PAS HIN-2012-014

CMS Lint (2011) = ~150 b-1 (|y|<2.4) Trigger: dimuon events at L1 (no constraints on muon momentum)

Use pseudo-proper decay lengthto estimate the b-hadron decay length

N.B.: discuss only prompt production in this talk