Manuel Calderón de la Barca Sánchez - The University of ...nuclear.ucdavis.edu/~calderon/Presentations/MCalderon-Nantes-Quark... · t~1-10 fm/c Collision, t=0 ... ITS and MTR Centrality

Manuel Calderón de la Barca Sánchez

Helmholtz Research School on Quark Matter Lecture Week on Heavy Flavor Subatech, Nantes 25 Oct 2015

Lecture Outline ! Why are we interested in Quarkonia in Heavy Ion Collisions?

! Measurements! ! Quantifying suppression/enhancement ! Introducing the Experiments ! How are Quarkonia measured in the experiments?

! Many results! Charm/bottomonium, RHIC, LHC, pp, pA, AA... ! Discuss data, predictions/expectations. ! What are the results? ! What have they taught us?

26-Oct-15 Manuel Calderón de la Barca Sánchez 2

Charmonium inside a QGP

! Key distinction between Quark-Gluon Plasma and normal nuclear matter:

! Color fields are manifest over nuclear distances ! Color Debye screening! ! Should prevent c-cbar states from binding.

! Same argument applies to b-bbar states.


The Charmonium Suppression Idea

! J/! suppression via color screening in a Quark-Gluon Plasma ! T. Matsui & H. Satz PLB178, 416 (1986), over 2000 citations!

! What do we mean by “screening”?

! Debye screening of the electrostatic potential:


Charmonium screening cartoon


screening cartoon

Production of Heavy Quark pair

Quarkonium meson forms

Heavy quarks propagate/interact in vacuum

Charmonium screening cartoon

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Ultra-relativistic Heavy-ion: At extremely high energy, initial state contains large number of colored partons, mostly gluons Partons deposit energy in large volume during collision. Color fields! Some high Q2 collisions also produce correlated heavy quarks.

Interaction between heavy quarks is modified in QGP. Color screening!

At freezeout, quarkonium state does not form.

Quarkonium in-medium ! An active field! ! Both in theory....

! Recent Lattice QCD Studies: Complex potential

! Suppression due to interplay of Screening, Landau Damping, singlet-octet transtions, threshold enhancement...

Burnier, Laine, Vepsalainen JHEP 0801 (08) 043, Beraudo, arXiv:0812.1130 Petreczky, Miao, Mocsy, Nucl Phys A 2011

! All effects studied rely on presence of a medium: QGP

! And in experiments... ! NA50, PHENIX, STAR, CMS, ALICE, ATLAS, LHCb...


Guidance from QCD: Lattice studies ! Lattice QCD on quarkonia: aim for a 1st principles insight into properties of in medium.


QQ

What We Know from Lattice

! Rapid rise of the energy density: ! liberation of new degrees of freedom

! Strong screening of static Q-Qbar free energy ! Screen at shorter distances with increasing T

rscr < rJ/! : “melting” of the J/! Manuel Calderón de la Barca Sánchez 9

Cheng et al (RBC-Bielefeld) PRD 77, 014511 (2008)

26-Oct-15

Heavy Quark Potential at High T Charmonium suppression:

! High T ! color deconfinement ! screening

! Screening prevents heavy quark bound states from forming!

! Lattice calculations confirm screening effects

! Screening: Re V ! Landau damping, gluodissociation,

gluon absorption (singlet-octet transition): Im V

! Both Re and Im contribute to Quarkonium Suppression

26-Oct-15

V ~ !"eff

rT = 0

V ~ !"eff

re!

rrD (T )

T >TC

Manuel Calderón de la Barca Sánchez 10

Burnier, Kaczmarek, Rothkopf PRL 114, 082001 (2015)

Color Debye-screening ! Bottom is heavy: use NR Quantum Mechanics (Schrödinger Eq.)

! Heavy quark potential for b quarks: screened at high T. ! Screening requires presence of

! Different states have different sizes/binding energy ! Sequential suppression pattern: a


!(1S) !(2S) !(3S)

Quarkonia as probes of QCD ! States are massive, produced early

pQCD can estimate production

! Sensitive to temperature and deconfined color fields: input from Lattice QCD ! Debye screening, Landau damping

!Re and Im V(r, T)

! Different states have different sizes/binding energy ! Sequential suppression


Caveat: Open Questions ! How is the heavy quark pair actually produced?

! What is the interaction between heavy quarks in vacuum and in a hot QCD medium?

! How do heavy quarkonia form and hadronize?

! Heavy ions collision are dynamic, not static. How does this affect the properties of quarkonia states?


Heavy ions collision are dynamic,

Measuring suppression

! Null hypothesis: AA = pp * N ! Quantifying enhancement/suppression in heavy-ion collisions.


Measuring key properties ! Produce medium in a collision.

! Want to measure its properties.

! Need probes! à la Condensed Matter physics.

! Difficulty: ! Medium does not “sit there” ! Need to produce probes ‘in situ’


Quark-Gluon Plasma,

t~1-10 fm/c

Collision, t=0

Measurable remnants: Hadrons, a few leptons All we know is inferred from them!

The Nuclear Modification Factor ! A way to compare yields

from p+p collisions to A+A collisions.

! General Idea: ! Measure yield/cross section in p+p collisions. ! Measure same process in A+A collisions. ! Simplest hypothesis: no modification due to nuclear effects. ! Leads to

! (A+A yield) = (p+p yield) x (Number of binary nucleon-nucleon collisions)

! Nuclear modification factor: Quantifies deviations from this simplest hypothesis.


Nucleus: A bunch of nucleons

Head on view Side view

RAA =! AA

Nbin! pp

26-Oct-15

•! Expectation: –! Peripheral collisions: Do not produce hot matter. –! Central collisions: Produce

•! Possible Ex.: MC Glauber model, b, Npart, Ncoll. Manuel Calderón de la Barca Sánchez 17

Peripheral collisions: Do not produce hot matter. Central collisions: Produce

Glauber model, b, Glauber model, b, Glauber N

Centrality in Heavy Ion Collisions ! “Centrality”: a

useful knob in our experiments

! Collisions can be ! Peripheral: barely touching, or ! Central: “head-on”

! Many “Participants”

Introducing the Experiments

! At SPS: NA38, NA50, NA60


PHENIX, muon arms ! J/! " µ+µ- ! 1.2 < |y| < 2.2

! Note: acceptance and efficiency is not the same in both arms

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STAR: Solenoidal Tracker

At RHIC

! Mid-rapidity detector: ! |!| < 1, 0 < " < 2#

! TPC: p, dE/dx ! TOF: ! BEMC: trigger, e ID ! MTD: trigger, µ ID

! Fully installed in 2014 ! behind magnet ! Precise timing ($~100 ps)

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Sánchez 20

Muon Telescope Detector Time of Flight

Barrel Electromagnetic Calorimeter

Time Projection Chamber

ALICE

! A Large Ion Collider Experiment Charmonia are measured down to zero pT

! forward rapidity (2.5<ylab<4) in the µ+µ- channel, using MTR, MCH and ITS

! mid rapidity (|ylab|<0.9) in the e+e- channel, using TPC and ITS Trigger system uses V0, ITS and MTR Centrality uses V0, ZDC


ZDC

V0

ITS

TPC

MCH MTR

ATLAS

! A A


Muon Spectrometer (MS) |"|<2.7

Inner Detectors

(ID) |"|<2.5

Event trigger: di-muon trigger with 2 GeV pT threshold Muon candidates: Successful combinations of ID and MS tracks.

LHCb

! Dedicated to beauty and charm physics Muons: 2 < " < 5


CMS

Dimuon: |y|<2.4 !: all pT, J/!: 3, 6.5 depending on y.


Charmonium Results

! A long history: SPS, to RHIC, to LHC ! Two decades worth of data,

measurements vs. : ! "s, centrality, rapidity, and pT , species

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J/! Production in pp

! PHENIX : consistent with pQCD predictions. ! Note: uncertainties of order 20%. ! All experiments have similar measurements for pp


arXiv:0906.2405

Experimental RAA, SPS & RHIC ! J/! nuclear modification

factor: ! yield in AA collisions relative to yield in pp

pp: baseline, no Debye screening ! scaled pp with number of binary NN collisions

! J/!-suppression pattern observed at SPS and RHIC

! RAA: Similar in magnitude

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J/ -suppression pattern

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Charmonium RAA vs. y. ! Forward rapidity data show more suppression than mid-rapidity

! Both show more suppression with higher Npart.


PHENIX PRL 98 232301 (2007)

RHIC: Mid-y, low and high pT

! PHENIX, measure to low pT ! STAR, pT > 5 GeV/c.

! Less suppression at high pT: consistent with screening. ! Suppression is still present for high pT J/y in central collisions.

! If due to in-medium energy loss, it is less pronounced than for light hadrons.


Mid-y J/! electron & muon measurements

! STAR low, high pT J/!#>ee. New: J/!#>µµ. ! Consistent results in both channels. ! Low pT more suppressed than at high pT ! Transport models including regeneration:

! qualitatively reproduce rise of RAA with pT. 26-Oct-15 Manuel Calderón de la Barca Sánchez 30

RA

A STAR PLB 722 (2013) 55 STAR PRC 90, 024906 (2014) Y.-p. Liu, et al. PLB 678 (2009) 72 X. Zhao et al. PRC 82 (2010) 064905

J/! RAA !s dependence at RHIC

! Forward region: 1.2 < |y| < 2.2 ! From 39 to 200 GeV, there is little change in the

suppression. ! Additional Hot matter effects: recombination of cc pairs.


J/! at RHIC: Some lessons ! Suppression seen, all experiments see centrality dependence.

! Little dependence with beam energy. ! Screening via higher T, Energy density would give larger suppression with increasing beam energy.

! Points to additional mechanisms. Recombination?


Experimental RAA, from RHIC to LHC

! Suppression is observed for central collisions ! Both forward and at midrapidity ! It is less pronounced at LHC than at RHIC:

! RAA(LHC)>RAA(RHIC)

! It shows no dependence on centrality for Npart > 70

Manuel Calderón de la Barca Sánchez 33 26-Oct-15

ALICE PLB 734 (2014) 314-327

Forward-y Mid-y

J/! RAA, pT dependence RHIC, LHC

! RAA at LHC is larger in the low-pT region. ! Consistent with model incorporating recombination


Models Compared to the ALICE data ! Statistical Hadronization Model (SHM)

Andronic et. al., JPG 38 (2011) 124081 ! Primordial charmonia are completely

suppressed in the QGP Charmonium production occurs at phase boundary by the statistical hadronization of charm quarks

! Transport Models (TM) ! TM1: Zhao et al., NPA 859 (2011) 114–125, ! TM2: Zhou et al., PRC 89 (2014) 054911 ! Continuous charmonium dissociation and

regeneration in the QGP, described by a rate equation

Comover Interaction Model (CIM) Ferreiro, PLB 731 (2014) 57

! Dissociation occurs by interaction with a dense co-moving partonic medium ! Regeneration is added as a gain term to the comover dissociation

! All models require a (re)combination component to describe the data ! All models also include cold nuclear matter effects (shadowing)


TM1: Zhao et al., NPA 859 (2011) 114–125,

Interaction Model (CIM) arXiv:1506.08804

J/! RAA vs. pT in centrality bins

! Transport models reproduce data reasonably well ! Note: different interplay btw suppression/regeneration ! Centrality dependence can help discriminate.

! TM1 has much higher RAA for low pT peripheral. ! Caveat: ALICE does not remove photoproduction contribution, which affects very peripheral bin.


arXiv:1506.08804 [nucl-ex] Most peripheral 40-90%

Most central 0-20%

J/! in AA: some lessons ! LHC higher RAA than at RHIC for most central collisions and low pT ! Taken as strong evidence for recombination/regeneration

! Key point: we need both facilities! RHIC & LHC ! To study the full thermodynamic behavior, we need to vary the initial conditions.

! Need data at many beam energies ! Big Question: are we sure that all the effects are from QGP, i.e. deconfined, hot quarks & gluons?


Documents

Manuel Calderón de la Barca Sánchez - The University of ...nuclear.ucdavis.edu/~calderon/Presentations/MCalderon-Nantes-Quark... · t~1-10 fm/c Collision, t=0 ... ITS and MTR Centrality