Double hypernuclei at PANDA M. Agnello, F. Ferro and F. Iazzi Dipartimento di Fisica Politecnico di Torino SUMMARY The physics of double-hypernuclei; Double strangeness production with antiprotons new way for 2-hypernuclei; Simulation of the physics: preliminary results many physical processes involved.
Double hypernuclei at PANDA. SUMMARY The physics of double-hypernuclei; Double strangeness production with antiprotons new way for 2 L -hypernuclei; Simulation of the physics: preliminary results many physical processes involved. M. Agnello , F. Ferro and F. Iazzi - PowerPoint PPT Presentation
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Double hypernuclei at PANDAM. Agnello, F. Ferro and F. Iazzi
Dipartimento di FisicaPolitecnico di Torino
SUMMARY The physics of double-hypernuclei; Double strangeness production with antiprotons
new way for 2-hypernuclei; Simulation of the physics: preliminary results
many physical processes involved.
Strange baryons in nuclear systems S=1S=1: -, -hypernuclei
• nuclear structure, new symmetries• The presence of a hyperon may modify
the size, shape… of nuclei• New specific symmetries
• hyperon-nucleon interaction• strange baryons in nuclei• weak decay
Initial state: SCR threshold: PTH,SCR 2.65GeV/c; production threshold: PTH,3.01GeV/c pbar momentum chosen: P(pbar) = 3 GeV/c (from theory (3 GeV/c) = MAX) Final state: no produced; two-body final state
0bar processes: annihilation (inside or outside production nucleus),decay- processes:
• deceleration inside nucleus through elastic nuclear scatterings• decay (negligible)
From pbar to D-Hypernucleus (step 1)- path inside residual nucleus. Results from simulation:
A non-negligible number of -’s undergoes a few scatterings a non-negligible fraction of -’s is decelerated below 800 MeV/c
P(-) distribution outside the Ga nucleus(Intranuclear scattering effects)
From pbar to D-Hypernucleus (step 2)
Energy loss and complete stop of- in secondary target
Assumptions: Two parallelepipedal targets (1 mm gap):
• - production target (gallium wire 4(cm) x 50 x 50(m2) , A=70)• hypernuclear target (diamond), 8 x 8 x 4 (thickness) cm3
beam spot diameter: 50 m
each - is given a lifetime , according to the distribution around the mean life at every deceleration step, the proper elapsed time interval is compared with ,
in order to determine whether the particle survives or not a complete stop is achieved in the diamond target: the stop position and the total
elapsed time are evaluated
P(-) distribution before C target(Intranuclear scattering + energy loss in Ga target effects)
Elapsed proper time before - entering C target
From pbar to D-Hypernucleus (step 2)
Energy loss (2105 simulated -’s). GalliumGallium production target.
Results:
I solution II solutionDecayed in Gallium 83 150
Decayed in the gap 5528 7879
Decayed in Diamond 98977 131700
Stopped in Diamond 197 3823Fraction stopped in Diamond 9.85E-4 1.91E-2
From pbar to D-Hypernucleus (step 2)
Energy loss (2105 simulated -’s). GoldGold production target.
Results:
I solution II solutionDecayed in Gold 90 186
Decayed in the gap 5752 8572
Decayed in Diamond 100203 131697
Stopped in Diamond 429 5770Fraction stopped in Diamond 2.14E-3 2.88E-2
Ga production target: expected ratesLet us assume the following parameters:
Luminosity L 1032 cm-2s-1; A = 70, Z = 31(pbar+nbar) 2 b at 3 GeV/c (Kaidalov & Volkovitsky)
(pbar+A) (pbar+n)A2/3(A-Z)/A p conversion probability, P 0.05 (Yamada, Hirata) probability of transition per event PT 0.5 level population fraction: PS 0.1 reconstruction efficiency: K 0.5 photo peak efficiency: 0.1 from simulation: stopped - fraction, f 9.8510-4 1.9110-
2We obtain (for Ga target):
Number of produced -: N = L 1600 Hz Number of stopped and detected -: Nstop NfK 0.79 15.3
s-1
Number of detected -hypernuclei: N NstopPPT PS (1.97 38.2)10-4 s-1 (per month: 510 9914;
UrQMD: 200)
Au production target: expected ratesLet us assume the following parameters:
Luminosity L 1032 cm-2s-1; A = 197, Z = 79(pbar+nbar) 2 b at 3 GeV/c (Kaidalov & Volkovitsky)
(pbar+A) (pbar+n)A2/3(A-Z)/A p conversion probability, P 0.05 (Yamada, Hirata) probability of transition per event PT 0.5 level population fraction: PS 0.1 reconstruction efficiency: K 0.5 photo peak efficiency: 0.1 from simulation: stopped - fraction, f 2.1410-3 2.8810-
2We obtain (for Au target):
Number of produced -: N = L 1600 Hz Number of stopped and detected -: Nstop NfK 1.71 23 s-
1
Number of detected -hypernuclei: N NstopPPT PS (4.3 57)10-4 s-1 (per month: 1114 14774)
Conclusions• Simulation of - production and stopping (based on INC-Like Model) has been implemented• Previous UrQMD rate prediction has been confirmed (slightly enhanced)• - & double hypernuclei high rate production seems feasible in PANDA
Future work• Optimizing the physical parameters
(production target, densities, geometry,…)• Simulating 0bar , +bar annihilations for trigger purposes• Simulating the conversion and decay for detection purposes• Producing spectra and distributions
to insert in the event generator of PANDA-MC• Exploring the experimental aspects (trigger, detection efficiency,...)