Measurements of the - PowerPoint Presentation

Slide1

Measurements of the meson production in Au+Au collisions at the STAR experiment

Oliver Matonoha

EPS-HEP 2017 Venice, Italy5—12 July 2017

for

the STAR collaboration

Czech Technical University in Prague

oliver.matonoha@fjfi.cvut.czSlide2

Outline

of

the talk

1

2

3

Heavy quarkonia as a QGP probe

The STAR experiment

Latest results in

p+p

,

p+Au

, and

Au+Au

collisions

at

RHIC

4

Comparison

with

LHC results and models

5

Summary

and

outlookSlide3

etc. are good

candidates to probe QGP

,

pairs

created mostly

before the QGP formation

Production cross-section in p+p collisions

can be calculated based

on pQCDDissociation by

colour screeningQuarkonium expected

to

dissociate

when

its

radius

exceeds

the

Debye radius

:

Sequential

meltingDissociation depends on the

quarkonium binding energyDifferent states expected to melt at different temperatures

QGP thermometer

Heavy

quarkonia

in QGP

etc.

T. Matsui, H. Satz, PLB 178 (1986) 416

A. Mocsy, EPJ C61 (2009) 705

H.

Satz

, IJMPA

 28 (2013)Slide4

Other effects also play a roleOther phenomena complicate the

measured quarkonium

suppression

Statistical recombinationCoalescence

of deconfined quarks

at QGP phase boundary

Cold nuclear matter

(CNM) effectsInitial

state: shadowing, energy loss

Final state: inelastic

interactions

with

hadrons



nuclear

break

-up

 co-

mover

absorption

Can be studied

in p+A collisionsFeed-down

RHIC 200 GeV

LHC 2.76 TeV

#

/ event

13

115

#

/ event

0.1

3

RHIC 200 GeV

LHC 2.76 TeV

13

115

0.1

3

I.

Das, QM2015, https://indico.cern.ch/event/355454/contributions/838966/

For at RHIC :no recombinationless co-mover absorption cleaner probe!

A. Emerick, X. Zhao, R. Rapp, EPJ A48 (2012) 72

Z.

Lin

, C.

Ko, PLB 503 (2001) 104Slide5

MTDBEMC

Magnet

TPC

Excellent

PID, full

coverage at

TPC (

Time

Projection

Chamber

)

:

tracking

,

p

measurement,

dE

/

dx

PIDBEMC (

Barrel Electromagnetic Calorimeter) :

trigger on and identify high-

lectronsMTD (

Muon Telescope Detector) :

< 0.5 and

~ 45%,

PID and

triggering

Upton, NY

STAR experiment

RHIC (

Relativistic

Heavy

Ion

Collider

)Slide6

Results from p+p and p+Au collisionsp+p :

precise baseline

for

comparison with Au+Au

collisions

 improved precision

:



consistent

with

the

Colour

Evaporation

Model (CEM)

prediction

p+Au :

quantification

of

CNM

effects

with

A.Frawley

,

T.Ullrich

,

R.Vogt

, PR 462 (2008) 125 Slide7

Signal in Au+Au collisions

Background sources:

 combinatorial background (estimated as

)



Drell

-Yan di-

leptons

,

semi-leptonic

decays

2014 data

2011 data

 Slide8

Results from Au+Au collisionsDi-muon and

di-electron

results consistent

with each other

within the

uncertainties

peripheral

central

Nuclear modification

factor

as a

function

of

mean

number

of

participants

☆

is

a

combination

of

★

results

results

combined

for

increased

statistical

precision | | stat. uncertainty□□ syst. uncertainty■■

common

norm. syst. unc.Slide9

RAA vs. Npart at RHIC

states

more

suppressed than

in central

collisions

 Slide10

Compare RHIC with LHC

states

more suppressed

than

in central

collisionsComparison with

LHC:  solid consistency

for



hint

of

less

suppression

for

at RHIC

than

at

LHC

CMS,

PRL 109 (2012)Slide11

Suppression vs  

Consistent

for

Signs

of less suppression

at high-

for

RHIC

vs. LHCSlide12

Comparison with modelsStrickland, Bazov

:No CNM, no regeneration

SBS (

Strongly Binding Scenario): fast

dissociation—potential

based on internal

energyWBS (Weakly Binding

Scenario): slow

dissociation—potential based

on free energy

Liu

,

Chen

,

Xu

,

Zhang

:

No CNM

Dissociation

only

for excited

states, suppression

of ground state due

to feed-down

Emerick, Zhao, Rapp

:

Includes

CNM, SBS case

 SBS

models

favoured

by the data

NPA 879 (2012) 25

PLB 697 (2011) 32

EPJ A48 (2012) 72Slide13

p+pImproved precision; consistent

with the

CEM model

p+AuQuantification of

the CNM effect

:

Au+Au

suppression at RHIC

is

similar

to

that

at

the

LHC

Direct

may

be

suppressed

;

better

understanding

of

CNM

effects and feed-down

contribution is needed

more

suppressed

than

in

the

most central collisions (sequential melting)

seem to be less suppressed at RHIC than at LHCResults can be used to impose constraints on the QGP temperature at RHIC

 Summary

OutlookAnalyses from other Au+Au data are underway  increase in statistics by about a factor of 2!

Thanks

for

your

attention

!Slide14

Back-up slidesSlide15

Results from p+p2015 dataSlide16

Results from p+Au2015 dataSlide17

Excited-to-ground-state ratio