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Double hypernuclei at PANDA

This summary examines the current status and future prospects of double hypernuclei physics, focusing on novel production techniques utilizing antiprotons. It covers the fundamental physics of double hypernuclei, including the dynamics of strange baryons and their interactions within nuclear systems. Emphasis is placed on double strangeness production methods, preliminary simulation results, and their implications on nuclear structure. The work by M. Agnello, F. Ferro, and F. Iazzi illustrates the complexities of hyperon-nucleon interactions and the characteristics of nuclear symmetries involved in these processes.

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Double hypernuclei at PANDA

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  1. Double hypernuclei at PANDA SUMMARY • The physics of double-hypernuclei; • Double strangeness production with antiprotons • new way for 2L-hypernuclei; • Simulation of the physics: preliminary results • many physical processes involved. M. Agnello, F. Ferro and F. Iazzi Dipartimento di Fisica Politecnico di Torino

  2. Strange baryons in nuclear systems • S=1: L-, S-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: X-atoms, X-, 2L-hypernuclei • nuclear structure • baryon-baryon interaction in SU(3)f • H-dibaryon • S=3: W-atom, (W-,LX-,3L-hypernuclei) J. Pochodzalla – LEAP 2003

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

  4. Double hypernucleus production techniques 1) Double Strangeness Exchange: K- + p ® K+ + X- • 106 K- on emulsion (®X- production ®X- capture ® hyper-fragment detection): few hypernuclei • @ BNL (AGS 1996): K- on 12C (diamond) (®scintillating fibers detector): 9000 stopped X- (in 4 months) • @ JHF: <7000 captured X- per day are expected 2) X- production from pbar: pbar + n ® X- + X0bar • pbarstop + A ® K*bar in nucleus ® K*bar + N in nucleus ® X-slow K + other • pbarflight + A ® X-fast + X0bar + (A-1) • low probability • X- to be strongly decelerated • X0bar is a strong signature

  5. Status of the X- production

  6. From pbar to Double Hypernucleus

  7. From pbar to D-Hypernucleus (step 1) Strangeness Creation Reaction (SCR): pbar + n + (A-1)®X- + X0bar + (A-1) • Initial state: • SCR threshold: PTH,SCR » 2.65GeV/c; p production threshold: PTH,p » 3.01GeV/c • pbar momentum chosen: P(pbar) = 3 GeV/c (from theory s(3 GeV/c) = MAX) • Final state: • no p produced; two-body final state • X0bar processes:annihilation (inside or outside production nucleus),decay • X- processes: • deceleration inside nucleus through elastic nuclear scatterings • decay (negligible)

  8. SCR kinematics (LAB frame) Two-body reaction with threshold: • max X- angle qmax(X-) » 0.3 rad »17.2o • two kinematical solutions with: 1.3 GeV/c £P(X-) £ 2.1 GeV/c 0.9 GeV/c £P(X0bar)£ 1.8 GeV/c 0.9 GeV/c £P(X-) £ 1.3 GeV/c 1.85 GeV/c £P(X0bar)£ 2.1 GeV/c 0 £q(X-) £q(X0bar) £ 0.3 rad »17.2o } I solution } II solution

  9. X-, X0barmomentum vs. X- angle

  10. P(X0bar) distribution after SCR

  11. X0bar angle after SCR

  12. From pbar to D-Hypernucleus (step 1) The X0bar fate | Kinematics parameters: • b(X0bar) » 0.8 • bct»6.5 cm • max q(X0bar) » 17.2o (0.3 rad) • High annihilation probability: • X0bar + nucleus ® K+ + K0 + X • or K0 + K0 + X • K+, probably forward-boosted, may be used for trigger purposes Simulation of X0bar annihilation and of K path is to be done

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

  14. From pbar to D-Hypernucleus (step 1) X- path inside residual nucleus. Results from simulation: • A non-negligible number of X-’s undergoes a few scatterings • a non-negligible fraction of X-’s is decelerated below 800 MeV/c

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

  16. From pbar to D-Hypernucleus (step 2) Assumptions: • Two parallelepipedal targets (1 mm gap): • X- production target (gallium wire 4(cm) x 50 x 50(mm2) , A=70) • hypernuclear target (diamond), 8 x 8 x 4 (thickness) cm3 • beam spot diameter: 50 mm Energy loss and complete stop of X- in secondary target • each X- is given a lifetime t, according to the distribution around the mean life • at every deceleration step, the proper elapsed time interval Dt is compared with t, 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(X-) distribution before C target (Intranuclear scattering + energy loss in Ga target effects)

  18. Elapsed proper time before X- entering C target

  19. From pbar to D-Hypernucleus (step 2) Energy loss (2×105 simulated X-’s). Gallium production target. Results:

  20. From pbar to D-Hypernucleus (step 2) Energy loss (2×105 simulated X-’s). Gold production target. Results:

  21. Ga production target: expected rates Let us assume the following parameters: • Luminosity L » 1032 cm-2s-1; A = 70, Z = 31 • s(pbar+n®XXbar) »2 mb at 3 GeV/c (Kaidalov & Volkovitsky) • S º s(pbar+A) » s(pbar+n)×A2/3×(A-Z)/A • X-p®LL conversion probability, PLL»0.05(Yamada, Hirata) • probability of transition per event PT»0.5 • level population fraction: PS»0.1 • reconstruction efficiency: eK»0.5 • g photo peak efficiency: eg»0.1 • from simulation: stopped X- fraction, fX»9.85×10-4 ¸ 1.91×10-2 We obtain (for Ga target): • Number of produced X-: NX = L×S»1600 Hz • Number of stopped and detected X-: Nstop»NX×fX×eK»0.79¸15.3 s-1 • Number of detected LL-hypernuclei: NLL»Nstop×PLL×PT ×PS×eg» » (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 » 1032 cm-2s-1; A = 197, Z = 79 • s(pbar+n®XXbar) »2 mb at 3 GeV/c (Kaidalov & Volkovitsky) • S º s(pbar+A) » s(pbar+n)×A2/3×(A-Z)/A • X-p®LL conversion probability, PLL»0.05(Yamada, Hirata) • probability of transition per event PT»0.5 • level population fraction: PS»0.1 • reconstruction efficiency: eK»0.5 • g photo peak efficiency: eg»0.1 • from simulation: stopped X- fraction, fX»2.14×10-3 ¸ 2.88×10-2 We obtain (for Au target): • Number of produced X-: NX = L×S»1600 Hz • Number of stopped and detected X-: Nstop»NX×fX×eK»1.71¸23 s-1 • Number of detected LL-hypernuclei: NLL»Nstop×PLL×PT ×PS×eg» » (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 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,...) • by using PANDA-MC

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