Study of hyperon-pion resonances from kaonic absorptions with KLOE Oton Vázquez Doce Excellence Cluster Universe, TU-Munich November 6, Catania, Resonance Workshop.

Oton Vazquez DoceStrangeness in medium with KLOE2 The DA  NE collider e+ e- beams at ~ 500 MeV/c Φ → K+ K- (49.1%) Almost monochromatic low-energy K - (~127 MeV/c) Low hadronic background due to beam characteristics (compared with hadron beam lines) Top luminosity reached during SIDDHARTA run: 4x10 32 pb -1 s -1

Oton Vazquez DoceStrangeness in medium with KLOE3 * DRIFT CHAMBER - 90% 4 He, 10% C 4 H 10 - entrance wall in carbon fiber ( 12 C ) - momentum resolution ~ 0.4% * ELECTROMANETIC CALORIMETER - σ E /E= 5.7%/√E (GeV) Almost full acceptancy 4π: K-K- K+K+   e-e- e+e+ ~ 0.1 % of K - stop in the 4 He + C 4 H 10 ~ 1% of K - stop in the 12 C 2004/2005 data: 2 fb -1 analized (90%) The KLOE detector

Oton Vazquez DoceStrangeness in medium with KLOE4 * DRIFT CHAMBER - 90% 4 He, 10% C 4 H 10 - entrance wall in carbon fiber ( 12 C ) - momentum resolution ~ 0.4% * ELECTROMANETIC CALORIMETER - σ E /E= 5.7%/√E (GeV) Almost full acceptancy 4π: K-K- K+K+   e-e- e+e+ ~ 0.1 % of K - stop in the 4 He + C 4 H 10 ~ 1% of K - stop in the 12 C 2004/2005 data: 2 fb -1 analized (90%) Active detector: THE GOOD: + Excellence acceptance + Excellence resolution + Charged+neutrals THE BAD -low statistics -interacting nuclei difficult to identify The KLOE detector

in-flight. Analysis of events in the 12 C entrance wall of the DC pp  K - stopped + 12 C → Σ + π - A KLOE: event selection  in 12 C Oton Vazquez DoceStrangeness in medium with KLOE5 (detected particles)

Analysis of events in the 12 C entrance wall of the DC → Σ 0 π 0 A  pp  I=0, free from  * background KLOE: event selection  in 12 C Oton Vazquez DoceStrangeness in medium with KLOE6 in-flight. pp  K - stopped + 12 C → Σ + π - A (detected particles) KLOE: statistical error MeV/c2 PDG: M Λ ± stat ± syst ( MeV/c 2 ) Λ → p + π - σ = ± MeV

Oton Vazquez DoceStrangeness in medium with KLOE7 K - stopped + A → Λp X’ in-flight pp (detected particles) KLOE: event selection  p in 4 He+C 4 H 10 Resolutions for events in GAS:

Oton Vazquez DoceStrangeness in medium with KLOE8 in-flight pp (detected particles) proton deuteron triton TOF mass (MeV/c 2 ) KLOE: event selection  p in 4 He+C 4 H 10 K - stopped + A → Λp X’ PID by TOF:

Oton Vazquez DoceStrangeness in medium with KLOE9 in-flight pp (detected particles) proton deuteron triton TOF mass (MeV/c 2 ) KLOE: event selection  t in 4 He+C 4 H 10 K - stopped + A → Λt X’ M  t (MeV/c 2 ) Direct formation 4NA cos   t Absorption rate ~ 0.06 ± 0.03% per K-  t sample in GAS ( 4 H+ 12 C) 119 events FINUDA: 40 events (world record) PID by TOF:

In-flight absorptions Oton Vazquez DoceStrangeness in medium with KLOE10 P K- (MeV/c) Kaon rarely tracked. Momentum for K- tracked in GAS events (for  p events) -> Contamination of in-flight events up to ~50% (lower for multi-nucleonic absorptions)

 Original objective: confirm or deny K - pp, K - ppn Objectives Oton Vazquez DoceStrangeness in medium with KLOE11

 Original objective: confirm or deny K - pp, K - ppn Objectives Oton Vazquez DoceStrangeness in medium with KLOE12 Theoretical work K - pp Strong attractive I=0 KN interaction favors discrete nuclear states high B and small Γ. How deeply is bound a kaon in a nucleus?

 Original objective: confirm or deny K - pp, K - ppn Objectives Oton Vazquez DoceStrangeness in medium with KLOE13 Experiments: DISTO LEPS-Spring8 HADES

 Original objective: confirm or deny K - pp, K - ppn  Study of resonances:  (1405  (1385) Objectives Oton Vazquez DoceStrangeness in medium with KLOE14

 Original objective: confirm or deny K - pp, K - ppn  Study of resonances:  (1405  (1385)  Qualitative and quantitative characterization of the  conversion process in 4 He and 12 C, cusp near to the  N threshold  Study of the multinucleonic absorption processes: 2NA, 3NA, 4NA. Objectives Oton Vazquez DoceStrangeness in medium with KLOE15

16 Oton Vazquez DoceStrangeness in medium with KLOE  p correlations in GAS (90% 4 He+10% C 4 H 10 )

17 Oton Vazquez DoceStrangeness in medium with KLOE  p correlations in GAS (90% 4 He+10% C 4 H 10 ) M Λp (MeV/c 2 ) - Low invariant mass: 1 Nucleon absorption followed by Σ/Λ nuclear conversion 1NA: K - N→Σ π -High invariant mass: 2NA : K - NN→ΛN 3NA: K-NN→ΛN ΣN→ ΛN

18 Oton Vazquez DoceStrangeness in medium with KLOE  p correlations in GAS (90% 4 He+10% C 4 H 10 ) M Λp (MeV/c 2 ) - Low invariant mass: 1 Nucleon absorption followed by Σ/Λ nuclear conversion 1NA: K - N→Σ π -High invariant mass: 2NA : K - NN→ΛN 3NA: K-NN→ΛN ΣN→ ΛN Quasi-free ( 4 He, 12 C) free! (H) or free! (H)

19 Oton Vazquez DoceStrangeness in medium with KLOE  p correlations in GAS (90% 4 He+10% C 4 H 10 ) M Λp (MeV/c 2 ) - Low invariant mass: 1 Nucleon absorption followed by Σ/Λ nuclear conversion 1NA: K - N→Σ π -High invariant mass: 2NA : K - NN→ΛN 3NA: K-NN→ΛN ΣN→ ΛN Quasi-free ( 4 He, 12 C) free! (H) or free! (H)

Λp preliminary fit M Λp (MeV/c 2 ) K-N → Σπ + Σp/Λp conversion in 4 He K-H → Σπ + Σp/Λp conversion in 12 C - No fragmentation (higher mass) - Residual fragmented (lower mass) K-NN → Λπp (higher mass) K-NN → Σπp (lower mass) K-NN → Σp + Σp/Λp conversion in 4 He K-NN → Λp (higher mass) K-NN → Σ 0 p (lower mass) Uncorrelated background Fit 3D (P Λ, P p, θ Λp ) +++ Data ---- Global fit preliminary Oton Vazquez DoceStrangeness in medium with KLOE20

preliminary Λp preliminary fit M Λp (MeV/c 2 ) K-N → Σπ + Σp/Λp conversion in 4 He K-H → Σπ + Σp/Λp conversion in 12 C - No fragmentation (higher mass) - Residual fragmented (lower mass) K-NN → Λπp (higher mass) K-NN → Σπp (lower mass) K-NN → Σp + Σp/Λp conversion in 4 He K-NN → Λp (higher mass) K-NN → Σ 0 p (lower mass) Uncorrelated background Fit 3D (P Λ, P p, θ Λp ) conversion in 4 He conversion in 12 C conversion after 2NA: more energetic conversion after 1NA +++ Data ---- Global fit 2NA direct production 21

22 Oton Vazquez DoceStrangeness in medium with KLOE  p correlations in GAS (90% 4 He+10% C 4 H 10 ) M Λp (MeV/c 2 ) - Low invariant mass: 1 Nucleon absorption followed by Σ/Λ nuclear conversion 1NA: K - N→Σ π ΣN→ ΛN Quasi-free ( 4 He, 12 C) or free (H )  +++  p correlated (missidentification and uncorrelated bkg. subtracted)

Oton Vazquez DoceStrangeness in medium with KLOE23 Y  Resonant VS Non-Resonant

KN→ (Y*?) → Y  how much comes from resonance ? Investigated using events in GAS: Oton Vazquez DoceStrangeness in medium with KLOE24 Y  Resonant VS Non-Resonant K - stopped/in flight + 4 He → Λ   3 He -S-wave non-resonant -P-wave resonant  (1385)

Oton Vazquez DoceStrangeness in medium with KLOE25 Y  Resonant VS Non-Resonant In collaboration with Prof. S. Wycech Atomic s-state capture assumed (from He bubble chamber data (Fetkovich, Riley interpreted by Uretsky, Wienke) and kaonic atoms experiments Coordinates recoupling enables for P-­wave resonance formation: --- S-wave non resonant --- P-wave S(1385)

Oton Vazquez DoceStrangeness in medium with KLOE26 P  (MeV/c) P π- (MeV/c) -Fiducial cut based in MC at-rest/ in-flight -Allows to remove  0 bkg. as well  ’direct formation’ in GAS volume Direct formation region  from secondary interaction (  nuclear conversion, etc)

Oton Vazquez DoceStrangeness in medium with KLOE27  ’direct formation’ in GAS volume P  (MeV/c) P π- (MeV/c) -Fiducial cut based in MC at-rest/ in-flight -Allows to remove  0 bkg. as well Direct formation region  from secondary interaction (  nuclear conversion, etc) * Sim. in-flight * Sim. at rest

Oton Vazquez DoceStrangeness in medium with KLOE28 Λ  Resonant VS Non-Resonant +++ Data Global fit Simultaneous fit (p   m     )  2 / df = 1.6 Absorptions in 12C (from Carbon wall data) Σ/Λ nuclear conversion K - N→Σ π ΣN→ Λ N

Oton Vazquez DoceStrangeness in medium with KLOE29 Λ  Resonant VS Non-Resonant Non-Resonant (in-flight) (at-rest) Resonant  (in-flight) (at-rest) Resonant/non-resonant absorption ratio: - at rest = 1.26 ± 0.06 (stat) In-fight/at-rest ratio = 1.9 ± 0.4 (stat) (consistent with  +  - data = 2.2 ± 0.05) +++ Data Global fit Simultaneous fit (p   m     )  2 / df = 1.6

Oton Vazquez DoceStrangeness in medium with KLOE30 Λ  Resonant VS Non-Resonant Non-Resonant (in-flight) (at-rest) Resonant  (in-flight) (at-rest) Resonant/non-resonant absorption ratio: - at rest = 1.26 ± 0.06 (stat) In-fight/at-rest ratio = 1.9 ± 0.4 (stat) (consistent with  +  - data = 2.2) +++ Data Global fit Simultaneous fit (p   m     )  2 / df = 1.6 The K - n→ Λ   S-wave amplitude | f s | (fm) is extracted Λ   data from J. Kim, Nucl. Phys. B 129 (1977) 1.

31 Λp correlations The extraction of the signal of a bound state in processes involving more than one nucleon can be done only with a scan in with and B.E. with a perfect description of the underlying processes (unless it is very narrow and with high formation rate). Nevertheles, the high invariant mass signal presents some difficulties to be explained with a simple 2NA simulation. ΣN/ΛN conversion process dominates both low and high invariant mass regions. This process can be described quantitatively and qualitatively exploring the YN interaction. The absorption data should require the description of a cusp effect at the  N threshold for the  /  conversion events in 4 He and 12 C Conclusions (I) Oton Vazquez DoceStrangeness in medium with KLOE

32  analysis Detailed calculation of the absorption process and  resonant and non-resonant formation have been performed  first measurement of resonant/non-resonant ratio in nuclear K - absorption 1.26 ± 0.06 allows to extract the K - n→ Λ   S-wave non-resonant amplitude 33 MeV/c 2 under threshold | f s |= 0.22 ± 0.01 (stat) ± 0.06 (syst) Outcome: extrapolate to the extraction of the  (1405) resonance from the  0  0,  +  - data in 4 He. Conclusions (II) Oton Vazquez DoceStrangeness in medium with KLOE --- Estimated K-H contamination

 analysis Detailed calculation of the absorption process and  resonant and non-resonant formation have been performed  first measurement of resonant/non-resonant ratio in nuclear K - absorption 1.26 ± 0.06 allows to extract the K - n→ Λ   S-wave non-resonant amplitude 33 MeV/c 2 under threshold | f s |= 0.22 ± 0.01 (stat) ± 0.06 (syst) Outcome: extrapolate to the extraction of the  (1405) resonance from the  0  0,  +  - data in 4 He. Conclusions (II) Oton Vazquez DoceStrangeness in medium with KLOE --- Estimated K-H contamination P  (MeV/c) P π- (MeV/c) K-H

 analysis Detailed calculation of the absorption process and  resonant and non-resonant formation have been performed  first measurement of resonant/non-resonant ratio in nuclear K - absorption 1.26 ± 0.06 allows to extract the K - n→ Λ   S-wave non-resonant amplitude 33 MeV/c 2 under threshold | f s |= 0.22 ± 0.01 (stat) ± 0.06 (syst) Outcome: extrapolate to the extraction of the  (1405) resonance from the  0  0,  +  - data in 4 He. Conclusions (II) Oton Vazquez DoceStrangeness in medium with KLOE ThanK - you!

SPARE Oton Vazquez DoceStrangeness in medium with KLOE35

Oton Vazquez DoceStrangeness in medium with KLOE36 KLOE data:  d  d sample in GAS 572 events

KLOE: Study of  in 12 C Mass of  0 reconstructed:  m ~ 18 MeV/c 2 Oton Vazquez DoceStrangeness in medium with KLOE37

-Resolution study with MC simulation and charged kaons decays: -Acceptance study with phase space K He -> Λ p n n MC simulation Reconstructed MC True phase space MC Normalization 1:1 (no efficiency evaluation) Minv Λp (MeV) Projection of acceptance function depending on (P Λ,P p,Minv Λp) on the Invariant mass plane Corrected MC with acc. Corr. KEK KLOE data: Λp analysis 38Oton Vazquez DoceStrangeness in medium with KLOE

 t correlations: Study of 4NA. Oton Vazquez DoceStrangeness in medium with KLOE39  t sample in GAS ( 4 H+ 12 C) 119 events FINUDA: 40 events (world record, published) M  t (MeV/c 2 ) Direct formation 4NA cos   t M  t (MeV/c 2 ) Simulations: NA ->  t NA ->  0t NA in 12C after breakup

 t correlations: Study of 4NA. Oton Vazquez DoceStrangeness in medium with KLOE40  t sample in DC-WALL ( 12 C) 439 events FINUDA: 40 events (world record, published) M  t (MeV/c 2 ) cos   t --- breakup events (extra proton track) Absorption rate ~ 0.04 ± 0.02 % per K- (preliminary)

41 Oton Vazquez DoceStrangeness in medium with KLOE   p event selection Two background sources: -Machine background (entering in the time selection window) - Events with  0 (double counting for those!)    (MeV/c 2 )

42 Oton Vazquez DoceStrangeness in medium with KLOE   p event selection Two background sources: -Machine background (entering in the time selection window) - Events with  0 (double counting for those!)    (MeV/c 2 ) --- Data --- Gaussian signal --- Machine bkg --- Pi0 bkg   mass resolution  MeV/c 2 K - stopped + X →   p X’ in-flight  (detected particles) pp

43 Oton Vazquez DoceStrangeness in medium with KLOE   p event selection --- Data --- Machine bkg --- Pi0 bkg +++ Subtracted signal GAS events DC-WALL 12 C events   p (MeV/c 2 ) Preliminary