Quarkonia in heavy-ion collisions with the CMS detector

Quarkonia in heavy-ion collisions with the CMS

detector

Nicolas Filipovic (LLR-Ecole Polytechnique)

ERC grant "QuarkGluonPlasmaCMS"

05/04/13 Quarkonia with CMS -‐ N.Filipovic 1

Au Menu Aujourd'hui

Currently working on kinemaBc dependences of ϒ(1S), Y(2S), Y(3S) producBon in PbPb Upsilon producBon in pp and pPb collisions (√sNN = 2.76, 5.02 TeV) Presented by Camelia Mironov at IS2013 (now!), also discussed here today


"Measurement of Upsilon resonances in heavy ion collisions (pPb, PbPb) with CMS": my thesis subject

The Compact Muon Solenoid


Acceptance coverage: 4.8 y units for muon chambers and tracker

10 y units for HCAL

PbPb event with large mulBplicity

efficient tracking down to p T > 200 MeV

'Global' muons are: Tracker muons matched with

'standalone' muons

ϒ -‐> μμ down to pT = 0 GeV/c

60 MeV/c2 mass resoluBon (y=0) separaBon of ϒ states

Quarkonia at high energy hadron colliders Quick introduction


ϒ(nS) are S-‐wave states of bb resonances Early stage of the collision: QQ pair creaBon. In hadron-‐hadron collisions: possibly several parton-‐parton process at the same Bme:

LO QCD diagram for Y producIon dominant at LHC

Differences among the ϒ(1S,2S,3S) states:

ProducBon (color-‐octet/singlet provenance)? FormaBon Bmes?

Feed-‐down (unknown fracBons)? 'Neighbourhood' relaBons?

SimilariBes among ϒ(1S,2S,3S) states:

Effect of energy-‐loss in medium, Nuclear parton distribuBon funcBons Negligible nuclear abs. at LHC in (pA)?

Branching fracBon to μμ ~ 3% All suppressed in PbPb at LHC


CMSPublic/PhysicsResultsHIN11011

What's been done up to now in PbPb RAA

PRL 109 (2012) 222301


How can Y's benefit from the new pp reference?

Thanks to the new pp reference, more accurate RAA(pT) and RAA(y) are possible Here, arBficially scaled to the published centrality-‐integrated value (real stat. uncertainty) Working on a double-‐differenBal study too (including NPart) 'Regional iteraBve tracking' on PbPb reconstrucBon: efficiency studies ongoing.

Breaking news


ϒ producBon in pp at √s = 2.76 TeV, pPb at √sNN 5.02 TeV


Dimuon spectrum of pPb at √sNN = 5.02 TeV

pPb Run Jan-‐Feb 2013 Lint = 31 nb-‐1

pp Run 09-‐14th Feb 2013 Lint = 5.4 pb-‐1

N(1S)pPb > 5500 in |yCM|< 1.93


Signal extraction

Signal extracBon in pp, pPb and PbPb same procedure Unbinned maximum log likelihood with 1S, 2S/1S, 3S/1S variables in the fit Signal: 3 Crystal-‐Ball funcBons (Gaussian with low-‐side tail replaced by a power-‐law) Background: errorFuncBon * exponenBal (all background parameters free)


Double Ratios ¡ pPb vs PbPb !

pPb vs pp: addiBonal effects in pPb than in pp, on the excited states compared to the ground state (significance <3σ) 20 % offset with 1 pPb vs PbPb: Much larger double raBos in pPb than in PbPb

Integrated measurement: split it!


Asymmetric collisions – event activity variables

η η

rapidity gap

Event acDvity is measured through : -‐  ET4<|η|<5.2: Energy deposit in forward HCAL -‐  NTrk

|η|<2.4 Charged-‐parBcle mulBplicity (pT>400 MeV/c) Binning in Ntrk and ET:

Goal : study a centrality-‐like dependence

Small overlap between pp and pPb


Event-activity variable ET4<|η|<5.2

In both pp, pPb: single raBo w.r.t. forward energy deposit is consistent with being flat


Event-activity variable NTrk|η|<2.4

the ϒ 'affects' the mulBplicity -‐ in both pp and pPb ~2 extra tracks in 1S events compared to 2S and 3S events the raIo

the mulBplicity 'affects' the ϒ -‐ acIvity around the Υ breaks the states

Decrease of Υ(nS)/Υ(1S) with increasing mulBplicit, both in pPb and pp!

Two drasBcally different ways of producing such a trend:


Event-activity variables : pp vs pPb vs PbPb

Need more PbPb data Almost no overlap between pPb and PbPb on the dimuon sample Centrality-‐integrated PbPb point well below pPb raBos


Self-normalized individual yields

For each of the three colliding systems, the slope is equal to 1 ! Suprising given the large difference in mean values One could suspect that mulBparton interacBons are involved in pp (high-‐mulBplicity)


Conclusions

When integrated over event acBvity larger than the ones measured in PbPb collisions. MulBplicity-‐dependence observed, slopes pp > pPb To understand pp, pPb and PbPb need more acBvity-‐related study of the Υ yields in pp collisions, as well as for more PbPb data allowing finer invesBgaBon of the most peripheral events.

Thank you


backup

tables for event acBvity binning


PbPb min bias fit


Upsilon in PbPb


Also, new pp data from 2013 (5.4 /pb) -‐  reduce the error bars (stat.) on the RAA -‐  KinemaBc studies of Y producBon is now ongoing

PbPb collisions at √sNN = 2.76 TeV A look at prompt J/ψ: suppression !


Two outstanding facts: •  strong centrality-‐dependent suppression of J/ψ,

•  At low-‐pT (forward region in CMS, 3 GeV/c threshold)

less suppression from ALICE (stats down to pT = 0) possible interplay of suppression and regeneraBon

CMS-‐HIN-‐12-‐014

Υ(nS) suppression in PbPb collisions at √sNN = 2.76 TeV

CMS:HIN-‐11-‐011


Y(1S): clear modificaBon Y(2S): strong suppression

Y(3S), we can (make an minimum bias RAA upper limit)

PRL 109 (2012) 222301

Backup (upsilon Double RaBo)


PRL 109 (2012) 222301

Backup (comp. Jpsi/Upsilon)


PRL 109 (2012) 222301

Quarkonia in heavy-ion collisions with the CMS detector

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