1. 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.

2. Strange baryons in nuclear systems S=1 S=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 The physics of double-hypernuclei S=2 S=2:  -atoms,  -, 2  -hypernuclei nuclear structure baryon-baryon interaction in SU(3) f H-dibaryon S=3 S=3:  -atom, (  -,  -,3  -hypernuclei) J. Pochodzalla – LEAP 2003

3. Double hypernuclei: present status 2  -hypernuclei have been already observed:

4. Double hypernucleus production techniques 1) Double Strangeness Exchange: K - + p  K + +  -  10 6 K - on emulsion (   - production   - capture  hyper-fragment detection): few hypernuclei  @ BNL (AGS 1996): K - on 12 C (diamond) (  scintillating fibers detector): 9000 stopped  - (in 4 months)  @ JHF: <7000 captured  - per day are expected 2)  - production from pbar: pbar + n  - +  0 bar  pbar stop + A  K * bar in nucleus  K * bar + N in nucleus   - slow K + other  pbar flight + A  - fast +  0 bar + (A-1)   low probability   - to be strongly decelerated   0 bar is a strong signature

5. Status of the  - production

6. From pbar to Double Hypernucleus

7. From pbar to D-Hypernucleus (step 1) Strangeness Creation Reaction (SCR): pbar + n + (A-1)   - +  0 bar + (A-1)  Initial state: SCR threshold: P TH,SCR  2.65GeV/c;  production threshold: P TH,   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   0 bar processes: annihilation (inside or outside production nucleus),decay   - processes: deceleration inside nucleus through elastic nuclear scatterings decay (negligible)

8. SCR kinematics (LAB frame)  max  - angle  max (  - )  0.3 rad  17.2 o  two kinematical solutions with: 1.3 GeV/c  P(  - )  2.1 GeV/c 0.9 GeV/c  P(  0 bar)  1.8 GeV/c 0.9 GeV/c  P(  - )  1.3 GeV/c 1.85 GeV/c  P(  0 bar)  2.1 GeV/c 0   (  - )   (  0 bar)  0.3 rad  17.2 o Two-body reaction with threshold: } I solution } II solution

9.  -,  0 bar  momentum vs.  - angle

10. P(   bar) distribution after SCR

11.  0 bar angle after SCR

12. From pbar to D-Hypernucleus (step 1) The  0 bar fate Kinematics parameters:   (  0 bar  0.8   c   6.5 cm   max  (  0 bar  17.2 o (0.3 rad) High annihilation probability:   0 bar + nucleus  K + + K 0 + X or K 0 + K 0 + X  K +, probably forward-boosted, may be used for trigger purposes Simulation of  0 bar annihilation and of K path is to be done |

13. From pbar to D-Hypernucleus (step 1)  - path in residual nucleus INC-like approach  (A-1) residual (excited) nucleus survives for a time longer than the time spent by  - during elastic scatterings  SCR reaction occurs uniformly in a spherical Ga nucleus (improvement: near the surface, to be done)   (  - ) is chosen uniformly in the CM frame of reference (improvement: Fermi momentum, to be done)  Elastic  T (  - N)  10 mb (Charlton, P.L. 32B; Müller, P.L. 39B)  Elastic d  /d   exp(B  t), B = 5 GeV -2 Assumptions:

14. 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

15. P(  - ) distribution outside the Ga nucleus (Intranuclear scattering effects)

16. 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(  m 2 ), A=70) hypernuclear target (diamond), 8 x 8 x 4 (thickness) cm 3  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

17. P(  - ) distribution before C target (Intranuclear scattering + energy loss in Ga target effects)

18. Elapsed proper time before  - entering C target

19. From pbar to D-Hypernucleus (step 2) Energy loss (2  10 5 simulated  - ’s). Gallium Gallium production target. Results:

20. From pbar to D-Hypernucleus (step 2) Energy loss (2  10 5 simulated  - ’s). Gold Gold production target. Results:

21. Ga production target: expected rates Let us assume the following parameters:  Luminosity L  10 32 cm -2 s -1 ; A = 70, Z = 31   (pbar+n  bar)  2  b at 3 GeV/c (Kaidalov & Volkovitsky)   (pbar+A)  (pbar+n)  A 2/3  (A-Z)/A    p  conversion probability, P   0.05 (Yamada, Hirata)  probability of transition per event P T  0.5  level population fraction: P S  0.1  reconstruction efficiency:  K  0.5   photo peak efficiency:    0.1  from simulation: stopped  - fraction, f   9.85  10 -4  1.91  10 -2 We obtain (for Ga target):  Number of produced  - : N  = L   1600 Hz  Number of stopped and detected  - : N stop  N   f   K  0.79  15.3 s -1  Number of detected  -hypernuclei: N   N stop  P   P T  P S     (1.97  38.2)  10 -4 s -1 (per month: 510  9914; UrQMD:  200)

22. Au production target: expected rates Let us assume the following parameters:  Luminosity L  10 32 cm -2 s -1 ; A = 197, Z = 79   (pbar+n  bar)  2  b at 3 GeV/c (Kaidalov & Volkovitsky)   (pbar+A)  (pbar+n)  A 2/3  (A-Z)/A    p  conversion probability, P   0.05 (Yamada, Hirata)  probability of transition per event P T  0.5  level population fraction: P S  0.1  reconstruction efficiency:  K  0.5   photo peak efficiency:    0.1  from simulation: stopped  - fraction, f   2.14  10 -3  2.88  10 -2 We obtain (for Au target):  Number of produced  - : N  = L   1600 Hz  Number of stopped and detected  - : N stop  N   f   K  1.71  23 s -1  Number of detected  -hypernuclei: N   N stop  P   P T  P S     (4.3  57)  10 -4 s -1 (per month: 1114  14774)

23. 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  0 bar,  + 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,...) by using PANDA-MC