Contents Timelike Formfactors of Hyperons HADES Upgrade PANDA Phase-0 in HADES Double Strange Hyperon Spectroscopy PANDA Phase-1 Summary

Radiative Hyperon Decays Decays to real and virtual photons sensitive to baryon structure: SLg : test of CP violation Hyperon Lee not measured at all: strong effects of vector mesons expected

Radiative Hyperon Decays Timelike (GM(q2), GE(q2)) complementary to Spacelike Low energy TL complementary to high energy TL (e.g. BES-III, CLEO) 𝐵𝐵→M 𝑒+𝑒− 𝐵1 →𝐵2𝑒+𝑒−

Timelike Hyperon Formfactors Timelike region recently measured in e+e- annihilation Measured |GM|2 a factor 10 larger than VMD Larger values for L than S indicate strong effects of (ud) quark correlations (S,I=0 for Λ) (S,I=1 for Σ) But, FF Analysis on resonance peak . . . K. Seth EPJ Web Conf. 95 (2015) 03033

Using HADES to Measure Y*Lee Proposed reaction: p p(A) Y (any hyperon) X e+e- X (BR~10-5)) High intensity AND energy proton beams (T = 4.5 GeV) Measured BR (Λγ) are large! (comparable to Δ→Nγ) Hyperon states are narrow HADES has excellent Λ and e+e- capabilities Upgrade challenges: Increase DAQ rate Improve g, e+e- efficiency (ECAL, RICH) Improve L efficiency (STS, FTOF)

HADES Upgrade

Forward Tracker (STS1/2+TOF) Reactions with low Q, and also the baryon from hyperon decay are strongly forward peaked ( Tracker + TOF Upgrade) Pions (and electrons) from Hyperon decay are emitted with a large polar angle ( HADES)

PANDA Phase 0 with HADES STS1/2 PANDA pre-series and prototype detectors for STS1/2 HADES measures the dileptons & mesons PANDA Straw Trackers for the baryon (Q<7˚) STS1: 640 tubes (use later as FT3/4) STS2: 900 tubes (use later as FT5/6) (4 double layers each) 76 cm

PANDA Phase 0 Experiments with HADES STS1 Jülich STS2 Cracow/Orsay FE and TRB Jülich Mechanics Orsay HV-System Cracow/GSI Gas-system Cracow/Jülich Software/Simul. Cracow/Jülich/Uppsala Construction in 2017 (on schedule) Installation in 2018 Operation 2018-2021

Physics Reach for L(1520) p+(p/C) pKL(1520)  pK Lee Λ(1520)→Λe+e-(3/2-→1/2-) transition Max. SIS18 energy 108 /s = 40 mb (assumed) ~ 500 evts/day reconstructed plus further increase due to upgraded RICH

Physics Program Plan: 30 days of proton beam at close to max. SIS18 energy Improve BR for S*0→Λg and S*+→S+g Establish BR for S*-→S-g and S*0→S0g Angular distributions of S0→Λg and S*0→Λg for a limit on P, CP violation (statistics??) Branching Ratio of S0(S*0)→Λe+e- Form Factors (most sensitive to magnetic) q2<(260) MeV2 BR and FF for Λ(1520)→Λe+e- Explore double strange - (1321) production (complementary to PANDA with pbar-p)

Multi-Strangeness Baryon Spectroscopy With PANDA

Quark Model for Ξ & Ω Ξ: many states predicted below 3 GeV compare 1/2+ and 1/2- excitation Ω: several states predicted between 2 and 3 GeV compare 3/2+ and 3/2- excitation Ξ U. Löring et al., EPJA 10 (2001) 447 Ω s.a.: M. Pervin, W. Roberts, PRC 77 (2008) 025202

Most Promising: Study Ξ Resonances very little known  rather high cross section find missing resonances determine branching to various decay modes: Ξ𝜋, Ξ 𝜋 + 𝜋 − , Ξ 𝜋 0 𝜋 0 , Λ 𝐾 − , Σ 𝐾 , Ξ𝜂, Ξ𝜂𝜋, Ξ 𝜂 ′ , Ξ𝜔, Ξ𝜙, … determine JP quantum numbers if possible strategy: select 𝑝 momentum to produce a specific resonance close to threshold

Ξ + Λ 𝐾 − final state: 𝑀 2 Λ 𝐾 − vs. 𝑀 2 Ξ + Λ dM Ξ + Λ 𝐾 − final state: 𝑀 2 Λ 𝐾 − vs. 𝑀 2 Ξ + Λ (bef. 4C kin. fit) σM(Ξ+) = 3.2 MeV frec ~ 2.5%, fbckg ~ 0.210-7 _ André Zambanini, Dissertation Univ. Bochum (2015)

_ pp  Ξ+Ξ(1820)-  Ξ+ΛK- Ξ + Λ 𝐾 − final state: 𝑀 2 Ξ + 𝐾 − vs 𝑀 2 Λ 𝐾 − Generated Reconstructed σM(Ξ+) = 4.0 MeV frec = 2.1% (updated) background suppression under study _ Jenny Pütz, Talk at FAIRNESS 2016

PANDA is a Factory for (Excited) Hyperons ! hyperon-antihyperon cross sections: 𝜎 𝑝 𝑝→ Λ Λ, Λ Σ, Σ Σ ≅10…100 𝜇b measured 𝜎 𝑝 𝑝→ Ξ Ξ ≅2 𝜇b measured 𝜎 𝑝 𝑝→ Ω Ω ≅2…100 nb predicted production rates at phase 1&2 luminosity 11031 s-1cm-2 : up to 108 Λ per day, ~107 Σ per day (charge state dep.) up to 2106 Ξ per day ~3104 Ω per day (assuming σ = 30 nb) at comparative energy above threshold, we expect the same order of magnitude for excited states

Ξ* / Ω* Studies within PANDA Physics Program Initial phase with lower Lumi Λ & Σ spectroscopy in parallel long runs to measure the X(3872) width in energy scan: in parallel, trigger for Ξ* and Ω* (peak finding) Mmax(Ξ*)  2.55 GeV (Mmax(Ω*)  2.20 GeV) later: long runs for threshold scan of DsDs(2317) Mmax(Ω*)  2.61 GeV Dedicated runs for JP determination of specific states!

Summary HADES – upgrade (Leptons and decay mesons) PANDA – Phase0 (decay baryon) On schedule for renewed SIS operation during 2nd half of 2018 Hyperon transition form factors at HADES Excited Double Strange Hyperons at PANDA

Competitiveness LHCb large number of Ξ and Ω observed spectroscopy in the light quark sector, JP determination? neutrals in final state difficult Belle 2 small Υ and 𝐵 branching to baryon-antibaryon final states GlueX, CLAS-12 small production cross section, no state seen above Ξ 1530 J-PARC 𝐾 − beam, but so far focussed on missing mass experiments PANDA is the best experiment for hyperon spectroscopy !

Baryon Spectroscopy Production of multi-strangeness baryons (unexplored, new territory, „Strangeness-Factory“) Octet X states: no partner of most N* states Decuplet X and W states: no partner of D* states PDG note on X resonances: “… nothing of significance on X resonances has been added since our 1988 edition.” What are the relevant degrees of freedom? ms~100 MeV mQCD~200 MeV Test of QCD at the transition Which are the relevant degrees of freedom? m S ≈100 MeV ~ Λ QCD ≈200 MeV Test of QCD at the transition Paola Gianotti

X(1820) High signal rates and high background rejection for excited double strange baryons

PANDA is a Factory for (Excited) Hyperons ! _ PANDA is a Factory for (Excited) Hyperons ! hyperon-antihyperon cross sections: 𝜎 𝑝 𝑝→ Λ Λ, Λ Σ, Σ Σ ≅10…100 𝜇b measured 𝜎 𝑝 𝑝→ Ξ Ξ ≅2 𝜇b measured 𝜎 𝑝 𝑝→ Ω Ω ≅2…100 nb predicted production rates at phase 1&2 luminosity 11031 s-1cm-2 : up to 108 Λ per day, ~107 Σ per day (charge state dep.) up to 2106 Ξ per day ~3104 Ω per day (assuming σ = 30 nb) at comparative energy above threshold, we expect the same order of magnitude for excited states

Open Questions Missing resonances Wrong masses, wrong sequence Relevant degrees of freedom? 3-quark? quark-diquark? meson-baryon dynamics from RPP 2014 / QM: S. Capstick, W. Roberts

Strange Partners Approximate SU(3) flavor symmetry N* & Δ states have partners in the strange sector focus on Ξ and Ω Ξ: as many states as N* & Δ together (1) Ω: as many states as Δ scrutinize our understanding of the baryon excitation pattern (1) in case of SU(3) symmetry !

Status of Ξ* Resonances: RPP 2014 Chin. Phys. C 38 (2014) 090001 ? Ξ(1820): Teodoro78 favors J = 3/2, but cannot make a parity discrimination. Biagi 87c is consistent with J = 3/2 and favors negative parity for this J value.

SU(6) x O(3) Classification RPP 2014: Chin. Phys. C 38 (2014) 090001 „Assignments for … Ξ(1820) and Ξ(2030), are merely educated guesses.“ Ξ(1690), Ξ(1950): T. Melde et al., PRD 77 (2008) 114002 decuplet: no Ξ*, no Ω* “… nothing of significance on X resonances has been added since our 1988 edition.” ?

J = 3/2 J = 5/2 Data on Ξ* States: Ξ(1530) The only reasonably well studied Ξ resonance: Ξ(1530) - decuplet g.s. JP = 3/2+ Г = 9…10 MeV decay: ~100% Ξπ BaBar measured the Ξ(1530)0 spin J = 3/2 in Λc+  Ξ- π+ K+ favor JP = 1/2- for Ξ(1690) Compare to Δ!! BaBar: B. Aubert et al., PRD 78 (2008) 034008

Early Physics: Expected Rates for Strange Baryons initial phase: 𝐿≅ 10 31 cm −2 s −1 instead of 𝐿≅ 2∙10 32 cm −2 s −1 nevertheless the Ξ Ξ production rate will be 𝑅 Ξ Ξ ≅10/s≅ 10 6 /d for Ω Ω production we expect 𝑅 Ω Ω ≅0.3/s≅ 3∙10 4 /d for excited states the cross section should be of the same order of magnitude as for the ground state for given 𝑠 − 𝑠 thr the detected rate depends on the specific decay mode (branching & reconstruction efficiency) e.g. 𝑝 𝑝→ Ξ + Ξ ∗− → Ξ + Ξ − 𝜋 0 → Λ 𝜋 + Λ 𝜋 − 𝜋 0 → 𝑝 𝜋 + 𝜋 + 𝑝 𝜋 − 𝜋 − 𝜋 0 assume 𝑏=0.5∙ 0.64 2 =0.2 and 𝜖= 5%  𝑅 𝑑𝑒𝑡 ≅ 10 4 /d

Recent Simulation & Analysis MC simulations & analyses: André Zambanini, PhD thesis U Bochum 2015 4.1 GeV/c pp  Ξ(1690)-Ξ+  K-ΛΞ+ Jennifer Pütz, PhD thesis on Ξ spectroscopy 4.6 GeV/c pp  Ξ(1820)-Ξ+  K-ΛΞ+ & c.c _