Physics with ALICE-PMD Basanta K. Nandi IIT Bombay For PMD collaboration

PMD 2  Distance from IP : 367 cm  Approx. 9 sq.m.  η Covergae : 2.3 to 3.9 Photon Multiplicity Detector (PMD) in ALICE

3 Honeycomb chamber (48×96 cells)  Cell depth : 0.5 cm  Cell cross-section : 0.23 cm 2  Total no. of cells : 220 K  Sensitive medium : Gas (Ar+CO 2 in the ratio 70:30) Photon Multiplicity Detector

4 E dep (a.u.) Energy deposition in PMD Hadron Photon Principle of Photon Multiplicity Detector ParticleCPVPRE PhotonNoYes Ch HadronYes

5  PMD measures: - Event-by-event number of photons produced in heavy-ion collisions - Spatial distribution (x,y) or ( ,  ) of photons  Physics Capabilities: - Pseudo-rapidity density - Limiting Fragmentation - Fluctuation in the ratio of N  /N ch in the common coverage of PMD & FMD - Azimuthal anisotropy and event plane determination - Charged particle multiplicity - Jet ??? Photon Multiplicity Detector

6  Particle production mechanism dN ch /d  = A x N part + B x N coll 19.6 GeV 130 GeV 200 GeV Hard processes contribution increases with centrality from ~30% to 50% in the mid-rapidity Q. What happens at higher energy?  Rapidity distribution of charged particles and photons gives the input to the theorist to validate their model  Hard process : N ch/ γ scales with N coll  Soft process : N ch/ γ scales with N part Au + Au at mid-rapidity Charged Particle pseudo-rapidity Density

7 Q. What happens in the forward rapidity for photons? Charged Particle pseudo-rapidity Density

8  At 0.9 TeV Phojet explains the data where as Pythia6D6T and Pythia6ATLAS underpredict.  At 7 TeV both Pythia and Phojet under-predict the data. Pseudo-rapidity distributions of Photons 900 GeV p+p7 TeV p+p ALICE PRELIMINARY

9  Limiting Fragmentation Q. Is the limiting fragmentation scenario valid for photons?  Particle production is independent of beam energy near beam rapidity

10 Limiting fragmentation (LF) behavior of photons  Limiting fragmentation behavior of photons seems to be inline with the earlier measurement.

11 Flow is a phenomenon seen in nucleus-nucleus collisions, which correlates the momentum distributions of the produced particles with the spatial eccentricity of the overlap region. azimuthal dependence of the pressure gradient. x z y pxpx pypy y x Reaction plane: z-x plane Elliptic Flow

12 Event Plane Determination from PMD  PMD event plane determination codes are in the repository for global use

13 FMD 1 FMD 3 FMD 2 Outer ing Inner ring Similar Eta acceptance of FMD2I and CPV FMD1 FMD2i FMD2 o FMD3o FMD3i IP Z-axis Beam line  = 2.3  = 3.5 PMD PRE CPV Charged particle measurement

14 CPV X-Y z = 0 z = 0 FMD  Principle – Three point straight line tracking  Necessity – Magnetic Field OFF data Method to determine primary Charged Particles

15 X Y R = √(x 2 + y 2 ) Method to determine primary Charged Particles

16 Charged particle measurement using CPV

17 Jet Study using PMD ? pp TPCPMD

18 Physics studies other than PMD  Fluctuation in mid-rapidity  K* measurement  Anti-Nuclei search

10% Centrality Bins5% Centrality Bins Centrality Dependence of ν dyn

20 Measurement of K*

21  Approximately 350 M events are analyzed  Various nuclei are nicely identified in ALICE 7 TeV Anti-Nuclei Search in ALICE

22 Summary: