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DiMuon Analysis with CMS detector using 2011 Heavy Ion Data

Vineet KumarPrashant Shukla

Nuclear Physics DivisionBARC Mumbai

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Outline of Talk

Physics Motivation of quarkonia analysis in heavy ion collisions.

Dimuons with CMS in 2010 Pb+Pb run

ϒ measurement with 2011 Pb+Pb data : paper in FR

Signal Extraction

Corrections

Results

J/ψ measurement with 2011 Pb+Pb data : Approval Today

Summary and outlook

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QGP and Colour Screening of Quarkonia

P e r t u r b a t i v e V a c u u m

cc

C o l o r S c r e e n i n g

cc

QCD Calculations indicate that, at a critical temperature around 170 MeV, strongly interacting matter undergoes a phase transition to a new state where the quarks and gluons are no longer confined in hadrons. Aim of Heavy Ion Collisions at high energies is to create, characterize and quantify the properties of QGP.

Color screening in QGP is expected to prevent the formation of quarkonium states indeconfined matter Different quarkonia states J/, ',

c, 1S,2S,3S) are expected to dissociate at different

temperatures, sequentially according to their radius. Measurement of a suppressed quarkonium yield may provide direct experimental sensitivity to the temperature of the medium created in high energy nuclear collisions.

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Experimental Puzzle at Lower energies

PHENIX, PRL 98 (2007) 232301, PRC 84 (2011) 054912SPS from Scomparin @ QM06

Similar J/ψ suppression at theSPS and RHIC

RAA

(RHIC, |y|<0.35) ≈ RAA

(SPS)

New observation at RHIC:

Suppression is more in forward rapidity region

RAA

(|y|<0.35) > RAA

(1.2<|y|<2.2)

Possible processes Initial state effects Cold nuclear matter effects Regeneration

What happens at the LHC? higher energy + higher luminosity more charm (more regeneration?) more bottom → a new probe ϒ states can be measured

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Quarkonia results with 2010 Pb+Pb Run

PRL. 106, 212301 (2011) CMS AnNote (055) 2010

PRL. 107, 052302 (2011) CMS AnNote (062) 2011

JHEP 1205 (2012) 063, CMS AnNote (062) 2011

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Dimuons with 2011 Pb+Pb data

2011 Pb+Pb at 2.76 TeV Total Luminosity 150 (µ b)-1 (20 times more than 2010) Detail study of ϒ states with event centrality Detail study of J/ψ suppression in many bins.

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ϒ raw yield extraction

3 Crystal-ball: Gaussian core & power law tail Free parameters: yield, resolution and mass for ϒ(1S) Fixed parameters: Resolution forced to scale with PDG mass ratios Background : 2nd order polynomial (PP) , exponential x error function (PbPb)

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Efficiency Vs Centrality of collision

Corrections mainly based on MC. Cross checked with TnP. Reconstruction efficiency almost constant with centrality of collision. Similar values for PP and PbPb collision. Efficiency ratio flat within uncertainties with centrality.

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Nuclear Modification Factor (RAA

)

Lpp

= 231 nb-1 N

MB = 1.13 billion

Centrality dependence observed with ϒ(2S) more suppressed thanϒ(1S)

ϒ(1S): 0.41±0.05±0.04 (0-5%)→ 1.01±0.18±0.12 (50-100%)

ϒ(2S): 0.11±0.02±0.06 (0-5%)→ 0.30±0.07±0.16 (50-100%)

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Double Ratio : [ϒ(ns) / ϒ(1s)]PbPb

/ [ϒ(ns) / ϒ(1s)]PP

Measure the relative suppression of the excited states relative to the ground state

In absence (by cancellation) of cold nuclear matter effects, ϒ(2S) is five times more suppressed than ϒ(1S) Within uncertainties centrality dependance is not very clear, on an average more suppressed in central collisions.

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Comparison to RHIC and J/ψ CMS

STAR measured RAA

of ϒ(1S+2S+3S) combined. We can measure R

AA separately for Y(1S) and Y(2S).

Suppression pattern in most central collisions, as expected from sequential melting

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J/ψ measurement with 150 µb-1 Pb+Pb Data

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J/ψ measurement with 150 µb-1 Pb+Pb Data

8.5K J/ψ with 6.5<pT<30GeV/c, |y|<2.4

Triggered by HLT_HIL1DoubleMu0_HighQ

Prompt J/ψ 12 centrality bins: 0-5, 5-10, ... 50-60, 60-100%

4 pT bin: 6.5-8, 8-10,10-13, 13-30 GeV/c

Non-prompt J/ψ 6 centrality bins: 0-10, 10-20,... 50-100%

4 pT bin: 6.5-8, 8-10, 10-13, 13-30 GeV/c

Differential: centrality&rapidity, centrality&pT

CMS Analysis Note CMSAN(246) 2012

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Prompt J/ψ RAA

First measurement high pT J/ψ, 12 centrality bins at 2.76 TeV.

Strong centrality dependence (more suppressed in central collisions)

More suppressed at hight pT ?

Less at forward rapidity ?

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Non Prompt J/ψ RAA

Unique measurement of non prompt J/ψ

Show same trend with centrality although entirely different physics process

First signature of b quark energy loss in strongly interactive medium.

More suppressed at hight pT and forward rapidity ?

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Summary and Plan

ϒ measurement : Double Ratio: First separate measurement, in HI collisions, of the relative suppression of ϒ(2S) and ϒ(3S) excited states wrt to the ground state. Ratio indicate ϒ(2s) is five times more suppressed than ϒ(1s).

RAA: ϒ(1S): Decrease of suppression from ~0.4 in 0-5% to ~1 in 50-100% ϒ(2S): First time measured in HI collisions , more suppressed than the ground state and still suppressed in 50-100% centrality bin. ϒ(3S): Smaller than 0.1 (95% C.L.)Study finished paper in FR. Will be submitted to PRL.

J/ψ measurement : Detailed study of J/ψ R

AA with centrality, pT and rapidity for Prompt and non Prompt.

Prompt J/ψ shows strong centrality dependence of suppression. First indication of b quark energy loss in medium with non prompt J/ψ Preparation of p+Pb run in Feb 2013 : Trigger Menu + MC

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Back Up slides

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Summary 1

First separate measurement, in HI collisions, of the relative suppression of ϒ(2S) and ϒ(3S) excited states wrt to the ground state.

Suppression pattern as expected in the sequential melting scenario.

Ratio indicate ϒ(2s) is five times more suppressed than ϒ(1s).

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Summary 2

RAA

: ϒ(1S) detailed centrality study decrease of suppression from ~0.4 in 0-5% to ~1 in 50-100%

RAA

: ϒ(2S) first time measured in HI collisions more suppressed than the ground state and still suppressed in 50-100% centrality bin

RAA

:ϒ(3S) smaller than 0.1 (95% C.L.)

Analysis finished. Paper under final reading by collaboration.Will be submitted to PRL.

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Outlook

CMS Data : Update of J/ψ R

AA with 2011 data.

More centrality bins for non prompt J/ψ Centrality bins in two rapidity bins for prompt J/ψ

Preparation for P+Pb run No QGP is expected there Measurement of initial state effect at LHC Nuclear matter effect

Phenomenology kinetic model of J/ψ regeneration

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ϒ yield extraction Functions

Npart , Ncoll and Taa values

Centrality Determination

2323

Acceptance of quarkonia in CMS

Antishadowing in LHC

B Fraction

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ϒ raw yield extraction

3 Crystal-ball: Gaussian core & power law tail Free parameters: yield, resolution and mass for ϒ(1S)tail parameter α (transition Gaussian→power-law) Fixed parameters: n (MC) exponent for tail description, resolution forced to scale with PDG mass ratios Background : 2nd order polynomial (PP) , exponential x error function (PbPb)

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ϒ raw yield : Pb+Pb and PP data

Using Bjorken scaling model, the time dependence of the energy density in the QGP medium is

the r dependence of the energy density is

Then the time a which temperature drops to TD =

t0 – formation time T

0 – initial temperature

A bottonium pair can escape the screening region rS if

r is the position of creation

Which gives the survival probability of the bottonium states as

ε (t )=ε ( t=t0 )( tt0

)ε (r,t0 )=ε0 [1− r

R ]1 /3

∣r+τ F pT

M∣>r S