Muons from the decay of charmed baryonsantibaryons

1
Muons from the decay of charmed
baryons/antibaryons

• Olga Piskounova
• ltP.N.Lebedev Physical Institutegt
• and Nikolai Nikitine
• ltSkobeltsyn Institute of Moscow State Univ.gt,
• Moscow

2
Plan

• Multiparticle production in the Quark-Gluon
  string model
• Spectra of Lc and antiLc in the recent
  experiments
• Procedure of spectra transformation into the
  laboratory system
• Charm decay calculations
• Lorentz boost and MC code
• Resulting muon spectra and asymmetry
• Summary

O.Piskounova

3
Quark-Gluon String Model

• QGSM is based on N-Pomeron exchange disgrams
  that lead to 2N quark-antiquark chains.
• Multiparticle production cross section are
  growing with the energy as
• sN(k)sP (1-e-zSN-1(zk/k!))/Nz
• where sP8pgP(0)e?D, ?ln(s/s0),
• z3gP(0)exD/(R 2aP(0)x).

O.Piskounova

4
Baryon production distributions

• Inclusive production cross section of hadrons H
  is written as a sum over N-Pomeron cylinder
  diagrams
• Distribution functions of Lc in p-p collisions
  are given by

5
Spectra of charmed baryons in pp
E781(SELEX) vs34GeV ? - ?c spectrum ?- anti?c

O.Piskounova

6
Transition to lab. system

• E010000GeV
• xds/dxds/dyc.m.s.ds/dy lab.s.
• ds/dEL EL-1ds/dyc.m.s(E0,mLc,EL)
• The procedure has been applied to
  calculations of antiproton spectra and gamma
  spectra from cosmic sources
• O.I.Piskounova Antiprotons in cosmic
  rays quark-gluon string model approach.
• Yad.Fiz.,47 (1988)749
• O.I.Piskounova About the shape of photon
  spectra from proton cosmic sources of high
  energy.
• Yad.Fiz.,51 (1990)1332

O.Piskounova

7
Description of the decay ?c ?Xs m nm

• This decay is described
• at partonic level
• c ? s m nm
• All calculations are similar to the calculations
  in the book L.B.Okun Leptons and quarks, 1981.

8
Decay width and probability
The differential decay width for c ? s m nm
transition
For the MC simulation the normalized matrix
element is used
9
Initial momentum configuration
10
MC procedure

• Nm0
• Generating of s,t pair, calculating of w(s,t)
• Accepting if rmdm(-1)ltw(s,t) in (s,t)-physical
  area
• Vector calculation p1,k1,k2 in rest frame of
  c-quark
• Random rotation
• Lorentz boost in ?c moving system
• Recording of event NmNm1

11
Resulting spectra of m and m-

• Muon spectra are following to the spectra of ?c.
• Muon charge symmetry is reproducing the leading
  asymmetry of charmed baryon spectra.

12
Asymmetry

• E0 10 5 10 6 GeV
• A (N- N-) / (N N-)
• O.Piskounova

13
Conclusions

• Spectra of all baryons in pp interaction of
• high energy have a specific form knee at
• EL close to m?, shoulder at EL0.1E0 and
• the slope of order E-1 in between
• Asymmetry between ? and ?- is of the same form
  as leading asymmetry between the spectra of
  ?c/anti?c
• This generator can be used for the calculation of
  spectra of muons and neutrino in ?b decays as
  well.
• O.Piskounova