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Jψ trigger study

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					Muon simulations for CBM at
SIS100

Anna Kiseleva1,2
Dipanwita Dutta1,3
Evgeny Kryshen2
Andrey Lebedev1,5
Mikhail Ryzhinskiy2,4


1 GSI, Darmstadt, Germany
2 PNPI, Gatchina, Russia
3 BARC, Mumbai, India
4 SPB SPU, Sankt-Petersburg , Russia
5 JINR LIT, Dubna, Russia
                                       1
Outline
• Motivation
• The CBM Muon detection system
• Event reconstruction of Au+Au@8AGeV
  –ω
• Event reconstruction of p+A@25-30GeV
  –ω
  – J/ψ
• Possible start version of the muon system
• Conclusions
                                              2
Nuclear matter physics at SIS100
• Physics case:
 – Nuclear matter equation-of-state at baryon densities up to 6 ρ0
 – In-medium properties of vector mesons
 – Charm production mechanisms at threshold beam energies
 – Charm propagation in nuclear matter
 – In-medium properties of D mesons
 – Multi-strange objects

• Observables:
 – Au+Au up to 11 AGeV
    • Hadrons (incl. collective flow)
    • Multi-strange hyperons
    • Dilepton pairs
 – p+A up to 29 GeV
    • D-mesons and charmonium
                                                                     3
Detector setups at FAIR

HADES at SIS100:                  CBM at SIS100/300:
• Electrons. hadrons, (photons)   • Electrons, muons, charm, hadrons,
                                    photons, exotica
• Nuclear collisions from
 1-10AGeV (max. Ni+Ni)            • Nuclear collisions from 4-45AGeV




                                                                        4
Muon measurements at SIS100




                              5
     Muon Chamber (MuCh)
     system
                                              < 5%
                                        occupancy
                                         for central
                                   Au+Au collisions

                        Fe    μ       at 25 AGeV
                                      w/o shielding
                                          min pad ~ 4 mm2
                                         max pad ~ 20 cm2

                             shielding
                                         Total number
                                          of channels:
                                              480 768
                             ≡ 13.5 λI


            ≡ 7.5 λI
                              μ+
low-mass vector meson
       measurements
      (compact setup)
                                                            6
Au+Au @ 8AGeV → ω + X
                ω → μ+μ




                           7
Acceptance
for ω mesons (MC)




Pluto    min.9 hits tracks   min.12 hits tracks




                                                  8
Results: full event reconstruction

     ω→μ+μ- + central Au+Au collisions at 8 AGeV



         N hits           min.9           min.12


      S/B ratio            0.05              0.1

      efficiency
                           1.65             0.95
           %


                                                   9
Muon system with ToF

       P2                (L, t) → β
m2 =
     (β × γ)2

     L
β =
    c×t

         1
γ =
      √1 – β2

              1
m2 = P2  (       - 1)
              β 2
                              MuCh ToF
                               (80 ps)

                                         10
      Results using ToF information
                         ω→μ+μ- + central Au+Au collisions at 8 AGeV



                             N hits          min.9            min.12


                          S/B ratio 0.05→0.09 0.1→0.14
           min.12 hits
                          efficiency
                                     1.65→1.2               0.95→0.8
                               %



with ToF

                                                                       11
p+C @ 30GeV → ω + X
              ω → μ+μ 




                          12
Results: full event reconstruction
                           ω→μ+μ- + p+C collisions at 30 GeV


                             S/B ratio             11
  1 ω→μ+μ- in 105 events
                            efficiency
                                                  4.3
                                 %




                                                               13
p+A @ 25GeV → J/ψ + X
              J/ψ → μ+μ




                           14
J/ψ phase-space distributions for
p+Au, p+C, Au+Au (HSD)




                                    15
              Results: full event reconstruction
                                                       p+Au          p+C
                                       collisions       @             @
                                                      25GeV         25GeV

                                       S/B ratio       B=0*          B=0*
J/ψ→μ+μ- + p+Au collisions at 25 GeV

               — background + J/ψ      efficiency
               — background                             16.4         21.4
                                            %
                                                    * 0 background pairs in J/ψ
                                                      mass region from 3.4109
                                                      events (see picture)
                                                                             16
S/B ratio calculation for p+A

• Background from Au+Au@25AGeV
• Normalization to the number of reconstructed
  background pairs in 3.4109 collisions :

   – NAu+Au: ~9105                    Np+Au
                             scale =
   – Np+C: 6                           NAu+Au


   – Np+Au: 78               scale =
                                       Np+C
                                       NAu+Au



                                                17
S/B ratio calculation for p+A
          Np+Au
scale =
          NAu+Au
                                   reconstructed
                                   background
                                   at Au+Au




                   scale
                   reconstructed
                   background
                   at p+Au           reconstructed
                                     J/ψ at p+Au




                                                     18
Results: full event reconstruction


                   p+Au    p+C
     collisions     @       @
                  25GeV   25GeV

      S/B ratio    187    1368

     efficiency
                  16.4    21.4
          %


                                     19
               J/ψ acceptance for p+Au@25GeV

                                                 Losses:
                                                 1. geometrical
                                                    acceptance 6° - 25°   STS
                                       STS
                         HSD                     2. magnet field           +
                         generated                                        MuCh
                                                 3. absorption in MuCh
                                                 4. reconstruction
                                                    efficiency

             STS                 STS+MuCh                      reconstructed
      (≥4 STS points)     (≥4 STS points+18 MuCh points)




10 000 events with J/ψ                                                           20
               J/ψ acceptance for p+C@25GeV

                                                 Losses:
                                                 1. geometrical
                                                    acceptance 6° - 25°   STS
                                       STS
                         HSD                     2. magnet field           +
                         generated                                        MuCh
                                                 3. absorption in MuCh
                                                 4. reconstruction
                                                    efficiency

             STS                 STS+MuCh                      reconstructed
      (≥4 STS points)     (≥4 STS points+18 MuCh points)




11 000 events with J/ψ                                                           21
Muon system start version




                            22
          Results:                                                                    5
                                                                                              6

                                                                                  4
          full event reconstruction                                       1 2 3
          (reduced number of stations)


J/ψ→μ+μ- + p+Au collisions at 25 GeV




                                           detector
    1-6    2-6     3-6    4-6    5-6   6               1-6   2-6   3-6   4-6   5-6        6
                                            triplets                                          23
New geometries




            without
            gaps




                      24
           Results:
           full event reconstruction

                                       6new                              (1+6)new

J/ψ→μ+μ- + p+Au collisions at 25 GeV

                                   (1+6)new




                                                                                       (1+6)new
                                              6new
                                                                                             6new
                                                 detector
     1-6   2-6     3-6    4-6    5-6      6       triplets   1-6   2-6    3-6   4-6   5-6   6     25
         Detectors for start version of MuCh




PNPI, St. Petersburg               JINR, Dubna
                                   PNPI, St. Petersburg



                 MICROMEGAS+GEM




                                   STRAW TUBES


                                                     26
Conclusions

•   Measurement of low-mass vector mesons in
    Au+Au collisions at 8 AGeV is feasible with
    compact MuCh (5 detector triplets and 5 absorber
    layers).

•   Excellent results for J/ψ measurements in p+C
    and p+Au with full MuCh (6 detector triplets and 6
    absorber layers).

•   Very good results for J/ψ measurements in p+C
    and p+Au with MuCh start version (only first and
    last detector triplet and 2 absorber layers).
                                                         27

				
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posted:5/19/2013
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