1 / 26

Low energy kaon scattering, an experimental overview

Low energy kaon scattering, an experimental overview. Alessandra Filippi INFN Torino. Low energy kaon scattering, a proposal for a new experiment at DA Φ NE. Workshop “Strangeness in Nuclei” – ECT* Trento, Oct 7th, 2010. Overview. Slow kaons at DA Φ NE: unique features

eli
Download Presentation

Low energy kaon scattering, an experimental overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Low energy kaon scattering, an experimental overview Alessandra Filippi INFN Torino Low energy kaon scattering, a proposal for a new experiment at DAΦNE Workshop “Strangeness in Nuclei” – ECT* Trento, Oct 7th, 2010

  2. Overview • Slow kaons at DAΦNE: unique features • The physics of charged kaon scattering: • Kaons • Antikaons • Open issues • Reasons of interest • IKON: an experiment at DAΦNE to perform precision cross-section measurements of in-flight low momentum kaons • VDET+KLOE: high precision general purpose detector • Feasibility studies (VDET simulations, kinematics, yields) • Synergy between IKON and AMADEUS • Summary

  3. K+p total K-p total K+p elastic K-p elastic K+d total K-d total K-n total K+n total K-n elastic DAΦNE DAΦNE Kaon-Nucleon scattering database • at low energy POOR WORLD DATABASE and LARGE ERROR BARS • DAФNE is the only world facility for near-threshold KN measurements

  4. K- K+ Φ 25 mrad e- e+ Experimental challenge: • Track kaonsand measure their momentum before their interaction • Track final state productsof K± scattering K±’s at DAΦNE: experimental conditions • Crab Waist Crossing: 25 mrad • (1020) produced with boost: ~12 MeV/c • Kaons from  decay: (1020) → K+K-, B.R. 48% • 115-141 MeV/c decay kaons • ~103 (1020) / s

  5. KLOE + VDET = IKON KLOE VDET: KLOE can host a vertex detector with a gas target (H2/D2), available room r=20 cm Same approach as AMADEUS

  6. K+N K+ = (us) • Existence of I=0,1 resonances, even below threshold • Strong coupling to many channels • Perturbative methods cannot be applied • Approximated models with coupled channels K-N K- = (us) The physics issues: K+N and K-N Different features of the K±N interaction call for different theoretical approaches • Small cross sections • Absence of resonances • Only elastic and CEX reactions possible • Studied with perturbative approaches or meson exchange models

  7. Jülich OBEP + Coulomb int. K+p, σtotal K+p, σelastic IKON pK(GeV/c) K+n, σelastic Jülich OBEP model IKON pK(GeV/c) K+N: present experimental situation I • TOTAL σ(K+p) on Hydrogen (I=1) • Dominant: elastic channel • No measurements pK< 150 MeV/c • TOTAL σ(K+n) on Deuterium (I=0,1) • Elastic + CEX reactions • Only source of I=0 KN interaction

  8. cosθCM cosθCM K+d → K+n ps K+p→K+p K+d → K+p ns cosθCM K+N: present experimental situation II • DIFFERENTIAL dσ/dΩ • K+p data: different trend between interactions in H2 and D2 • K+d: disagreement with theoretical predictions, both on p and n • General lack of low momentum measurements • K+d: no data < 342 MeV/c

  9. Precision measurement of KN Σ-term • More sensitive to the nucleon strangeness content than πN σ-term • Existing measurements very old and with large errors • Precision improvement: factor >5 with σ evaluations @ 10% Why new K+N measurements needed? • Low energy data crucial totune Chiral SU(3) theories • Better understanding of SU(3) at low energy • Fix low energy parameters • I=0 K+N scattering lengths • Known at 10%, based on data > 130 MeV/c • Nuclear phase shift sign (+/-) • Make “educated guess” of higher energy behaviour (Θ+)

  10. Scattering cross sections for elastic & inelastic processes Hadronic branching ratios close to threshold Data for below threshold resonance excitations: Σπ spectra Energy shift & width of kaonic atoms K-N interaction: overview IKON • NO ChPT • Baryonic resonances, I=0,1:Λ(1115), Σ(1190), Σ(1385), Λ(1405)… • Non-perturbative coupled-channel approach to describe all aspects of the K-N interaction • Low-energy data crucial input to enhance the predicting power of the KN models • Lack of experimental constraints close to threshold • scarcely selective models • poor below-threshold predictivepower • Exp.data with inconsistencies • No model able to account for them IKON IKON SIDDARTHA

  11. K-p → K-p K-p → K0n ~80 mb ~30 mb K0n threshold, 89 MeV/c 89 K-p →Σ+π- K-p →Σ-π+ >100 mb ~50 mb CC Model by Borasoy, Meißner, Nißler (2006), 1σ C.L.bands K-p →Λπ0 K-p →Σ0π0 ~40 mb ? ~50 mb ? ? ? K-N cross sections: available data & best fit Experimental data with 20% precision at most

  12. Produced below the K- N thr. • γp → Λ(1405) K* • K-p → Λ(1405) γ • K-p → Λ(1405) π0 • K-d → Λ(1405) n Small σ K-d Bauer 1977 KLOE KLOE Λ (1405) observed via its Σπ decay Σ±π∓decay: topology of secondary vertex • Σ0π0decay forbidden to Σ*(1385) IKON IKON ANKE 2008 M(Σ0π0) (GeV) Excitation of resonances below threshold: the Λ(1405) case - • Σπ measured lineshapes not reproduced satisfactorily by models yet • Old experiments measured Σ±π∓channels only, at high momentum • New results by ANKE & CLAS, also on Σ0π0 • More data still needed

  13. Direct scattering double scattering (2 steps) pK = 130 MeV/c Resonant contribution π+Σ- Quasi elastic π0Σ0 K-d scattering : a tool to observe Λ(1405)? At low momentum forward emitted neutrons help separating the elastic peak from the Λ(1405)→Σπ signal D. Jido et al. arXiv:1008.4423v1 [nucl-th]

  14. K±elastic scatteringon protons: K± p→K± p • K± quasi-elastic scattering on neutrons: K± d → K± np • K± elastic scattering on deuterons: K± d→ K± d • InelasticK- reactions on protons close to threshold (Y prod.) • K- p → Λπ0 • K- p → Σ±π∓,Σ0π0 • InelasticK- reactions on protons close to threshold (Y prod.) • K- p → Σ±π∓,Σ0π0 • Inelastic K- interactions on deuterons close to thr. (Y prod.) • K- d → YN π (Y = Λ, Σ) • Charge-exchange reactions (threshold: 89 MeV/c) • K- p →K0 n, K+ n → K0 p • K0L p → K+ n • Λ(1405) production in D2: K-d → Λ(1405)n → Σ±π∓n,Σ0π0n • Regeneration reaction: K0L p → K0Sp Summary: possible Kp(d) measurements All of them will be collected at the same time

  15. VDET TRACKING • Finesegmentation • Resolution below 50 μm • secondary vertex reconstruction • Very low mass • minimize ΔE & multiple scattering • Capable of operating in magnetic field (B=0.6 T) • TARGETS • Solid targets (CH/CD) • Active (trigger) • Very thin ( ~500 μm) • Background from C • Gaseous (H2/D2) • Large dimension (~2 cm) • High pressure (~2-3 bar) • Mylar walled (beware! Material budget) • Clean vertex identification IKON IKON • PARTICLE ID. • Charged Particles: mass identification (dE/dx) • Highly ionizing kaons • Outgoing protons • Outgoing pions (MIPs) • Neutral particles • γ’s & Neutrons • TRIGGER • Fast trigger required on incoming K+K- pairs • Thin segmented scintillator (500 μm) – mat. budget! • Self-triggering Si modules IKON IKON KLOE KLOE Experimental setup: general requirements

  16. Proposed VDET architecture I • Sensor type: double sided micro-strip based on Silicon technology • 200 μm x (~6 x 5 cm2) modules • state-of-the-art: 300 μm thickness • Spatial resolution: < 50 μm • Wide dynamic range for mass discrimination (1-20 MIPs) • Cylindrical symmetry around beam axis • large angular coverage • 100 equal modules arranged in prisms

  17. Proposed VDET architecture II tgt F(1020) K+ K- Si Si Si Si Si • 2 Inner layers • discrimination and reconstruction of K-K+ tracks coming from Φ’s (primary vertex) • 3 Outer layers • discrimination and reconstruction of K-,K+,π-,π+,p tracks coming from the interaction of K-K+ pairs in the target (interaction vertex)

  18. 3 Outer layers: 12.4 cm long 200 μm thick H2 gas target 2.5 cm thick 13 cm Y 2 Mylar foils 100 μm thick 13 cm X 2 Inner layers: 6.2 cm long 200 μm thick Beam pipe (Be) 350 μm thick Simulations and feasibility studies Igeometry

  19. Simulations and feasibility studies IIbeam and primary kaons Z • Φ generation with the present phase space configuration (Crab Waist) • Φ → K+K- decay • Beam spread: σz ~ 1.5 cm • Magnetic field: 0.6 T • Realistic VDET geometry • Simulations with Virtual MonteCarlo Tools (Geant3 + Geant4 engines) 1st Si layer 3rd Si layer Beam spread along z: ± 3.25 cm inner layers ± 6.5 cm outer layers

  20. 10000 generated K- (K+) at rest sin2θ @ the target Material Budget: Be Pipe 500 μm Si 2×200 μm pkrange accessible to measurements @ the outmost layer Generated @ Φ vertex Material Budget: Be Pipe 500 μm Si 4×200 μm H2 2.5 cm K- (K+) momentum distribution (MeV/c) • Measurements @ • 2-3 momenta: • 122 ± 10 MeV/c • 102 ± 10 MeV/c • < 95 MeV/c • (possibly) Simulations and feasibility studies III 75%: K+K- acceptance 46%: generated kaons reaching the outmost layer (decay)

  21. Simulations and feasibility studies IVspecific energy loss Energy lost in Si layers • Simulation of energy loss in 200 μm sensors: • Every layer can easily mass discriminate kaons from MIPs • Same technique as applied in FINUDA

  22. Simulations and feasibility studies Vkaon multiple scattering (picture not to scale) Z coord Si Si Si Si Si tgt 2σ ~0.7cm ~3° K± Θ 13 cm Y coord cm angular uncertainty due to Coulomb scattering: Θ~ 3 - 4° FWHM cm VDET with 100 μm pitch OK

  23. Simulations and feasibility studies VIK±N→K±N elastic scattering, kinematics and yields Coulomb dominance p Lab frame MeV/c β K- K- α low σ 127 MeV/c K- p Differential xsections measurable in the angular range 4o -75o 75o Cos α 3 fb-1 enough to perform precision measure-ments

  24. Simulations and feasibility studies VIIK-d→ Σπn @ Λ(1405) peak 4 fb-1 necessary to collect a statistically significant bulk of data (8 months data taking) With 4 fb-1: differential cross section for K±d scattering feasible in 9 momentum bins with a 6% stat. err./bin

  25. IKON for AMADEUS • Tracking of both K+ andK- is vital to determine cleanly the K- vertex, get rid of background from K+ decay particles and to get a correct beam normalization • With the proposed setup targets can be easily changed • Adding thin degrader foils: K-stop physics at hand

  26. Summary and Conclusions • DAΦNE is at present the only world facility where low momentum kaon scattering studies can be performed • Missing data • Needed inputs for low energy strong interaction theories • First feasibility studies performed: geometry, detector requirements, reaction kinematics, multiple scattering and energy loss effects, expected yields • Si Vertex-Detector + KLOE spectrometer & calorimeter • Full know-how on Silicon Detectors, reduced R&D phase needed • IKON only possible integrating with AMADEUS • Time scale fitting to KLOE/DAΦNE schedule for the next 3-4 years

More Related