Proposal on NICA SPD design (for consideration)

Proposal on NICA SPD design (for consideration)

SPIN 2013, Prague, July 7 -13, 2013

Valery Rodionov

Joint Institute for Nuclear Research Dzhelepov Laboratory of Nuclear Problems

Outlook

1) Drell-Yan kinematical distributions;2) Preliminary view of Spin Physics Detector (SPD);3) Conclusion.

ADVANCED STUDIES INSTITUTE SYMMETRIES AND SPIN, NICA-SPIN-2013, Prague, July 7 - 13, 2013

In order to contaminate in the dimuon mass spectrum the background from two sources (physics: D-meson, J/ and decays to ± X and combinatorial: and K to µ decays) the cleanest region to study Drell Yan is M> 4 GeV/c2 .

Drell-Yan kinematical distributions


Available phase-space for DY

MC DY: PYTHIA 6.1 generated DY events at pp @s = 24 GeV;

-parton distribution functions CTEQ5L;

- MC Sample: 500K events.

require almost 4π geometry for SPD

The distributions of the single muon polar angle and the angle between muons in the Drell-Yan pair .



Momentum distributions of the single muon from the DY pair with the invariant mass Mµµ >2 GeV/c2 and Mµµ >4 GeV/c2 for different angular intervals looking from the beam intersection point.



Expected statistics for clear DY :

With average luminosity L=1 x 1032 cm-2 s-1 expected event rate (an upper estimation):at M> 2 GeV/c2 ~1900 event/dayat M> 4 GeV/c2 ~900 event/dayReport by R.Akhunzyanov

Main detector requirements:

•Almost 4 geometry;•precision vertex detector;•precision tracking system ;•precision momentum measurement;•good particle identification capabilities;•high trigger rate capabilities.

Preliminary view of SPD


Silicon Microvertex

Central Tracker(Straw Tube Tracker)

Muon Detectors

Particle Identification

Tracking

Calorimetry

EMC

approx. size: 6x6 m



Silicon Microvertex DetectorOutside the beam pipe. Several layers of double sided silicon strips can provide a precise vertex reconstruction and tracking of the particles before they reach the general SPD tracking system. The design should use a small number of silicon layers to minimize the radiation length of the material. With a pitch of 50-100 µm it is possible to reach the spatial resolution of 20-30 µm. Such a spatial resolution would provide 50-80 µm for precision of the

vertex reconstruction. This permits to reject the secondary decay vertexes.

Central Tracker STTThe resolution of reconstructed momentum from the spatial trajectories p / p ~ 1 - 2 % (using dE/dx measurement for PID);Coordinate resolution <150 μm per plane;Low material of ~1% X/X0 (all tubes) in the radial direction;High rate capability -> drift time <100ns

EM CalorimeterPhoton energy range 0.1- 10GeV.Taking into account the space limitation in the barrel region, the total length of module of the ECAL should be less than 50 cm. The required energy resolution < 10.0%/√E (GeV).The latest version of the electromagnetic calorimeter (ECAL) modules, developed at JINR for the COMPASS-II experiment at CERN, can be good candidates for ECAL at SPD. These ”shashlyk” type of modules utilise new photon detectors – Avalanche Multichannel Photon Detectors (AMPD). AMPD can work in the strong magnetic field. Talk “A new electromagnetic calorimeter for COMPASS-II” by Anfimov Nikolay.

Preliminary detector requirements



Solenoid

The maximum magnetic field of ~1T over a length of about 3.2m and a diameter of 1.8m. The field

homogeneity is foreseen to be better than 2% over the volume of the vertex detector and central

tracker.

Muon detectors

The muon system which uses range system (RS) technique to register muons in laminated iron absorber and is aimed for identifying the primary muons and their separation from background contamination originated mostly from primary low-momenta pions and decay muons. The RS structure is a well known solution for both, detecting the muons stopped by the absorber and those crossing the iron. It is worth mentioning that such a structure may also serve as a coarse hadron calorimeter at NICA energies.The combination of responses from ECAL, RS and momentum reconstruction can be used for the identification of electrons, hadrons and muons in the energy range of NICA SPD .

For detailed information see Technical Design Report for PANDA Muon System (GSI, FAIR).



1) Preliminary Conceptual design for Spin Physics Detector at NICA was

proposed for consideration;

2) We kindly encourage the participation of scientists in the project;

3) A detailed MC studies is in progress.

Conclusions


The muons traversing the iron absorber are only subject of ionization energy losses until they are stopped .For pion case the situation is quite different. The pion passing through the absorber has the competing processes of ionization energy loss and showering due to the strong interaction in absorber.

At such small energies a pion could have “muon-like” pattern (for certain percentage) because of two processes: 1) pion could pass through the RS due to the ionization losses process only, giving the same RS depth as in muon case; 2) a muon from pion decay may get almost the same layer of RS absorber.

Proposal on NICA SPD design (for consideration)

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