Photon multiplicity @ rhic cucu 200 gev
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Photon Multiplicity @ RHIC CuCu 200 GeV. Monika Sharma Sunil Dogra Surjeet Singh Neeraj Gupta. Outline of the presentation. STAR experiment Photon Multiplicity Detector Recent results from charge particles Comparison of STAR-PMD results from AuAu 62.4 GeV & CuCu 200 GeV

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Photon Multiplicity @ RHIC CuCu 200 GeV

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Photon multiplicity @ rhic cucu 200 gev

Photon Multiplicity @ RHIC CuCu 200 GeV

Monika Sharma

Sunil Dogra

Surjeet Singh

Neeraj Gupta


Outline of the presentation

Outline of the presentation

  • STAR experiment

  • Photon Multiplicity Detector

  • Recent results from charge particles

  • Comparison of STAR-PMD results from AuAu 62.4 GeV & CuCu 200 GeV

  • Outlook & summary

Monika Sharma, QGP workshop, 5-7 Jan 2006


The star experiment

The STAR experiment

The STAR (Solenoidal

tracker At RHIC)

experiment at

Relativistic Heavy

Ion Collider (RHIC) is

designed to search

for different signals of QGP formation.

Monika Sharma, QGP workshop, 5-7 Jan 2006


The photon multiplicity detector

The Photon Multiplicity Detector

Preshower detector with fine granularity

Two planes : Veto +Pre

- shower.

η coverage : -2.3 – - 3.9

Total no. of cells: 82,944

Distance from vertex : 540 cm

Cell cross section : = 1.0cm2, depth 0.8cm

Readout : GASSIPLEX + C-RAMS

Monika Sharma, QGP workshop, 5-7 Jan 2006


Photon multiplicity rhic cucu 200 gev

Area of the detector : 4.2m2

Weight of the detector : 900 kg

Φ coverage : 2π

Detector design criteria :

Confine charged particle hits to

single cell.

Reduce cross-talk : stop δ-rays

with in a cell.

Uses a gas mixture of 70%Ar+30%CO2.

Monika Sharma, QGP workshop, 5-7 Jan 2006


Principle of preshower

Principle of Preshower

Photons passing through the

converter initiate an

electromagnetic shower &

produce large signals on

several cells of the

sensitive volume of the

detector. Hadrons normally

affect only one cell &

produce a signal

representing minimum ionizing particles.

Detector

γCLUSTER

Monika Sharma, QGP workshop, 5-7 Jan 2006

ISOLATED CH PARTICLE HIT


Techniques of pmd data analysis

Techniques of PMD data analysis

  • ADC distribution of isolated cells is studied to calculate the gain of each cell.

  • Gain is normalized to ensure uniformity over the entire detector.

  • Photon counting efficiency & purity in photon samples are calculated from simulation (HIJING+GEANT).

  • Photon discriminating threshold 3MIP &NCell> 1 is now applied to identify photons.

  • Geometrical acceptance correction factors are applied to the data to correct for any dead region of the detector.

Monika Sharma, QGP workshop, 5-7 Jan 2006


Results for star pmd data run v cucu 200 gev

Results for STAR-PMD dataRun V CuCu 200 GeV

Monika Sharma, QGP workshop, 5-7 Jan 2006


Centrality selection is star

Centrality Selection is STAR

275K events were used in the presnt analysis

Monika Sharma, QGP workshop, 5-7 Jan 2006


Pseudorapidity distribution of photons cucu 200 gev

Pseudorapidity Distribution of photons (CuCu 200 GeV)

STAR preliminary

Upper limit on systematic

Error ~ 24%

Monika Sharma, QGP workshop, 5-7 Jan 2006


Comparison of results from phobos charge particles

Comparison of results from PHOBOS (Charge Particles)

Charge particle production at forward rapidities are independent of

system size

Monika Sharma, QGP workshop, 5-7 Jan 2006


Previous star pmd results

Reference : PRL 95, 062301 (2005)

First results of photon multiplicity measurement were shown.

Photons are observed to follow a centrality independent limiting

fragmentation scenario.

Photons and pions

follow an energy

independent limiting

fragmentation behaviour.

Previous STAR-PMD results :

Monika Sharma, QGP workshop, 5-7 Jan 2006


Pseudorapidity distribution per participant pair

Pseudorapidity distribution per participant pair

STAR preliminary

STAR preliminary

Pseudorapidity distribution per participant pair is

independent of centrality. Results agree with previous

STAR-PMD Photon 62.4 GeV results!!!

Monika Sharma, QGP workshop, 5-7 Jan 2006


Limiting fragmentation

Limiting Fragmentation

  • Number of particles produced per participant pairs as a function of

    ή-ybeam is independent of beam energy.

  • Why limiting fragmentation?

  • At higher energies target fragments seen in lab frame reach a limit in momentum space.

Monika Sharma, QGP workshop, 5-7 Jan 2006


Particle production at forward rapidities is independent of centrality as well as system size

Particle production at forward rapidities is independent of centrality as well as system size

STAR preliminary

Monika Sharma, QGP workshop, 5-7 Jan 2006


Photons and pions follow an energy independent limiting fragmentation behaviour

Photons and pions follow an energy independent limiting fragmentation behaviour

STAR preliminary

Monika Sharma, QGP workshop, 5-7 Jan 2006


Summary outlook

Summary & Outlook

  • Results of photon multiplicity measurements at RHIC in the pseudorapidity region 2.3 <= ή <= 3.7 are shown.

  • Photon production per participant pair is found to be approximately independent of centrality in this eta region.

  • The comparison of Au+Au and Cu+Cu most central collisions indicate that the pseudorapidity density per participant pair does not depend on the size of the two colliding nuclei.

Monika Sharma, QGP workshop, 5-7 Jan 2006


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