Study of benchmark process Study of benchmark process

pp + + ppbarbar J/J/ΨΨ + X + X l l ++l l -- + X+ X

(( ll = = μμ, e ), e ) (E (E beambeam = 14 GeV) = 14 GeV)

A.N.SkachkovaA.N.SkachkovaG.D.AlexeevG.D.Alexeev

N.B.SkachkovN.B.Skachkov(JINR, Dubna)(JINR, Dubna)

22

This process is of interest for the muon system from the view point of its geometrical

acceptance.

For this reason we have concentrated our study on kinematical, mainly angular, distributions.

To get an idea about these distributions we have used, as for the first step, PYTHIA 6.4 event

generator with its parameters adjusted for the PANDA energies.

33

J/J/ΨΨ production processes production processes

421) 421) g g g g cc¯ [ cc¯ [33S S 1 1 (1)(1) ] g ] g ll ll + X+ X

422) 422) g g g g cc¯ [ cc¯ [33S S 1 1 (8)(8) ] g ] g llll + X + X

423) 423) g g g g cc¯ [ cc¯ [33S S 0 0 (8)(8) ] g ] g ll ll + X+ X

424) 424) g g g g cc¯ [ cc¯ [33P P J J (8)(8) ] g ] g llll + X + X

425) 425) g q g q cc¯ [ cc¯ [33S S 1 1 (8)(8) ] q ] q llll + X + X

426) 426) g q g q cc¯ [ cc¯ [33P P J J (8)(8) ] q ] q ll ll + X + X

427) 427) g g g g cc¯ [ cc¯ [33S S 1 1 (1)(1) ] q ] q ll ll + X + X

428) q q428) q q¯̄ cc¯ [ cc¯ [33S S 1 1 (8)(8) ] g ] g ll ll + X+ X

429) 429) q qq q¯̄ cc¯ [ cc¯ [11S S 0 0 (8)(8) ] g ] g ll ll + X + X

430) q q430) q q¯̄ cc¯ [ cc¯ [33P P J J (8)(8) ] g ] g llll + X + X

1) q1) q i i q q i i¯̄ ̽̽ c c c c¯ ¯ J/ J/ΨΨ l l ++ll - - + X+ X

86 ) g g 86 ) g g J/ J/ΨΨ + g + g l l ++ll - - + X + X R.Baier and R.Rücke, Z.Phys. R.Baier and R.Rücke, Z.Phys. C19C19 (1983) 251(1983) 251

106) g g 106) g g J/ J/ΨΨ + + l l ++ll - - + X + X M.Drees and C.S.Kim, Z.Phys.M.Drees and C.S.Kim, Z.Phys. C53 C53 (1991) 673(1991) 673 431) g g 431) g g cc¯ [cc¯ [33P P 00 ( (11) ] g) ] g ll ll + X + X

432) g g 432) g g cc¯ [cc¯ [33P P 11 ( (11) ] g) ] g llll + X + X

433) g g 433) g g cc¯ [cc¯ [33PP 2 2 ( (11) ] g ) ] g ll ll + X+ X

434) g q 434) g q cc¯ [cc¯ [33P P 00 ( (11) ] q ) ] q ll ll + X + X

435) g q 435) g q cc¯ [cc¯ [33P P 11 ( (11) ] q) ] q llll + X + X

436) g q 436) g q cc¯ [cc¯ [33PP 2 2 ( (11) ] q ) ] q llll + X + X

437) q q 437) q q cc¯ [cc¯ [33P P 00 ( (11) ] g) ] g ll ll + X + X

438) q q¯ 438) q q¯ cc¯ [cc¯ [33P P 11 ( (11) ] g) ] g llll + X + X

439) q q¯ 439) q q¯ cc¯ [cc¯ [33PP 2 2 ( (11) ] g) ] g llll + X + X

G.T.Badwin, E.Braten and G.P.Lepage, Phys.Rev. D51 (1995) 1125

[Erratum: ibid D55 (1997) 5883];

M.Beneke, MKrämer and M.Vänttinen, Phys.Rev.D57 (1998) 4258;

B.A.Kniehl and J.Lee, Phys.Rev. D62 (2000) 114027

44

PYTHIA 6 allows a proper account of the relativistic kinematics during the simulation,

but

it doesn’t give well determined cross section value for the case of J/Ψ production at the

low energies

(which is depend on some internal MCparameters, such as the limitation on the

phase space integration)

55

The main contributions to the cross section give The main contributions to the cross section give the next processes:the next processes:

1)1) q qi i qqii¯ ¯ ̽̽ c c¯ c c¯ J/ J/ΨΨ ll+ + ll - - + X + X428)428) q q q q¯̄ cc¯ [ cc¯ [33S S 1 1

(8)(8) ] g ] g ll+ + ll-- + X + X430)430) q q q q¯̄ cc¯ [ cc¯ [33P P J J

(8)(8) ] g ] g ll+ + ll-- + X + X

The maximum cross section value (obtained by PYTHIA 6.4 The maximum cross section value (obtained by PYTHIA 6.4 simulation) is simulation) is

σσ = = 20.75 pb 20.75 pb that corresponds to that corresponds to

358.5 events / day 358.5 events / day

for the Efor the E beam beam = 14 GeV = 14 GeV and Luminosity = 2*10and Luminosity = 2*105 5 1/mb*sec (= 2*101/mb*sec (= 2*1032 32 cmcm-2 -2 secsec-1-1))

66

Background QCD processes for the Background QCD processes for the ¯̄q q q q l l ++l l -- oneone

The generation was done with the use of more than 20 QCD subprocesses existed in PYTHIA (including The generation was done with the use of more than 20 QCD subprocesses existed in PYTHIA (including the signal one the signal one ¯̄q qq q l l ++l l -- ). ).

The main contributions come from the following partonic subprocesses:The main contributions come from the following partonic subprocesses:

q + g q + g q + g q + g (gives (gives 50%50% of events with the of events with the σσ == 4.884.88 mb); mb);

g + g g + g g + g g + g (gives (gives 30%30% of events with the of events with the σσ == 2.962.96 mb); mb);

q + q’ q + q’ q + q’ q + q’ (gives (gives 18%18% of events with the of events with the σσ == 1,75 1,75 mb);mb);

q + q bar q + q bar g + g g + g (gives (gives 0.6%0.6% of events with the of events with the σσ == 5.89 E- 02 5.89 E- 02 mb);mb);

¯̄q + q q + q l l++ + l + l-- (has (has 0.00005%0.00005% of events with the of events with the σσ == 5.02 E- 065.02 E- 06 mb);mb);

The simulation was done within approximation when particles are allowed to decay

in cylinder volume R =2500 mm , L=8000 mm

77

Applied cutsApplied cuts

To separate signal leptons from thoseTo separate signal leptons from those from pion’s decaysfrom pion’s decays

We select the leptonsWe select the leptons withwith EEl l > 0.2 GeV, PT> 0.2 GeV, PTll > 0.2 GeV > 0.2 GeV We select the events with only We select the events with only 22 leptons leptons

It gives pure signal events by cost of It gives pure signal events by cost of 1.7% loss1.7% loss

ll

Muon and electron distributions (and cross sections)Muon and electron distributions (and cross sections) look the same within PYTHIA simulation look the same within PYTHIA simulation

88

Signal Signal ll± : (± : (ll = = μμ,e),e)

00 ≤ E ≤ Ell ≤ ≤ 1010 GeV, GeV,

< E< Ell > = > = 4.4 4.4 GeV GeV 00 ≤ PT≤ PTll ≤ ≤ 22 GeV, GeV,

< PT< PTll > = > = 1.2 1.2 GeV GeV

PTPTll peakpeak = = 1.41.4 GeV GeV

< < ΘΘl l > = > = 27.2 27.2 °°

some some ΘΘll > > 9090°°

l l -- - left, - left, l l ++ - right: - right:

99

Signal Signal ll± :± :

00 ≤ E ≤ Eslow slow ≤ ≤ 55 GeV, GeV,

44 ≤ E ≤ Efast fast ≤ ≤ 1010 GeV GeV 00 ≤ PT≤ PTslow/fast slow/fast ≤ ≤ 22 GeV, GeV, PTpeak = PTpeak = 1.41.4 GeV GeV

1515oo < < ΘΘslowslow < < 140140oo ΘΘslow slow

peak peak = = 2525oo

00oo < < ΘΘfastfast < < 2626oo

ΘΘfast fast peak peak = = 1212oo

LEFT - Less energetic (slow), RIGHT - more energetic (fast)

1010

EEll”slow””slow”/E/E

ll”fast” ”fast” correlationscorrelations

1111

ΘΘ ll”slow””slow” / /ΘΘ ll”fast” ”fast” correlationscorrelations

Max of cos (l+,l-) is at ≃ 0.75 that

corresponds to an angle ≃ 42 o

1212

ΘΘll/E/Ell distributions fordistributions for“slow” leptons (left) and “fast” leptons “slow” leptons (left) and “fast” leptons

(right)(right)

1313

the possible events loss due to the the possible events loss due to the muon system cuts:muon system cuts:

9090o o cutcut 5.3 %5.3 %

6060o o cutcut 18.0 %18.0 %

A special interest had been attracted to the angular distributions of muons from J/Ψ

decay,

that shows

1414

The interesting problem of The interesting problem of specification the value of the cross specification the value of the cross section is postponed for the future.section is postponed for the future.

It may happen that to solve this It may happen that to solve this problem another than PYTHIA problem another than PYTHIA generator should be used.generator should be used.

1515

SummarySummary We have studied 50000 events generated with PYTHIA for We have studied 50000 events generated with PYTHIA for

the beam energy of 14 GeVthe beam energy of 14 GeV J/J/ΨΨ output output μμ, e, e range within range within 0 <0 < ΘΘll << 140 140 °,°, 00 ≤ E ≤ Ell ≤ ≤ 10 10 GeV, GeV, 00 ≤ PT≤ PTll ≤ ≤ 22 GeV. GeV. It looks that J/It looks that J/ΨΨ decay muons do not impose any new decay muons do not impose any new

special requirements for PANDA muon systemspecial requirements for PANDA muon system compared to muons from MMT/DY processcompared to muons from MMT/DY process

The generated PYTHIA events can be available on the web The generated PYTHIA events can be available on the web (mail to Anna.Skachkova@cern.ch)(mail to Anna.Skachkova@cern.ch)