Baryon Spectroscopy in COMPASS p p p f π + π p s p p p f K + K p s. Alex Austregesilo for the COMPASS Collaboration

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1 Baryon Spectroscopy in COMPASS p p p π + π p s p p p K + K p s Alex Austregesilo or the COMPASS Collaboration XIV International Conerence on Hadron Spectroscopy München, June 7 E 8 Supported by

2 Outline Introduction Event Selection Invariant Mass Distributions Outlook on Partial Wave Analysis Summary A. Austregesilo Baryon Spectroscopy at COMPASS /9

3 The COMPASS Experiment COmmom Muon and Proton Apparatus or Structure and Spectroscopy Setup Fixed target experiment at CERN SPS Twostage magnetic spectrometer Tracking, calorimetry, particle ID SM target + RPD SM E/HCAL COMPASS CEDARs RICH 9 GeV/c Secondary Hadron Beam 97% π, % K on lh, Pb, Ni, W targets 75% proton, 4% π +, % K + on lh target A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

4 Production Mechanism Central Production: Diractive Dissociation: Data primarily recorded to study the ormation o gluerich meson resonances at central rapidities No bias introduced by the principal trigger (diractive trigger) high contribution o diractive dissociation o the beam proton in analogy to pion beam data [c.. COMPASS presentations in Light Mesons session] A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 4/9

5 Baryon Spectroscopy Overview o light baryon spectrum Motivation Hadroproduction complementary to existing photo and electroproduction experiments (CLAS, CBELSA,..) High resolution spectrometer with lat acceptance Large data set High mass and high angular momentum states poorly known **** Existence is certain, and properties are at least airly well explored *** Existence ranges rom very likely to certain, but urther conirmation is desirable and/or are not well deined ** Evidence o existence is only air * Evidence o existence is poor [PDG, 7/8] A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 5/9

6 Event Selection Diractive trigger Exactly one primary vertex in target outgoing charged tracks charge conservation Beam proton (CEDAR) RICH identiication π + or K + Exclusivity Energy sum Φ angle between orward system and recoil particle very low background primary vertex X /cm Events /.5GeV/c primary vertex Z /cm COMPASS 8 p p p π + π p s Φ correlation Total Energy o p π + π p s 5 4 A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 6/9

7 Particle Identiication E RPD Ring B (MeV) COMPASS Recoil Proton Identiication Energy loss o recoil particle vs. velocity Very clean proton signal β Final State Particle ID Distinction between positively charged particles in orward direction RICH (Ring Imaging CHerenkov) detector Proton ID not eective in this kinematic range π + /K + identiication A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 7/9

8 p p p π + π p s A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 8/9

9 Invariant Mass o p π + π System 8 COMPASS 9 p p p π + π p s W ( % o 9) Invariant Mass o p π + π Unambiguous assignment o resonances diicult or example: N(44)P, N(5)D, N(55)S and N(65)S, (7)D, N(7)P, N(7)P A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 9/9

10 Invariant Mass o p π + π System 8 COMPASS 9 p p p π + π p s W ( % o 9) Invariant Mass o p π + π Unambiguous assignment o resonances diicult or example: N(44)P, N(5)D, N(55)S and N(65)S, (7)D, N(7)P, N(7)P Spin Parity (= Partial Wave) Analysis A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 9/9

11 Invariant Mass o Subsystems COMPASS 9 p p p π + π p s W ( % o 9) ρ (77) (98) (7) COMPASS 9 p p p π + π p s W ( % o 9) Invariant Mass o p π + π Invariant Mass o π + π A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

12 Invariant Mass o Subsystems COMPASS 9 p p p π + π p s W ( % o 9) ρ (77) (98) (7) COMPASS 9 p p p π + π p s W ( % o 9) Invariant Mass o p π + π Invariant Mass o π + π () COMPASS 9 p p p π + π p s W ( % o 9) () COMPASS 9 p p p π + π p s W ( % o 9) Invariant Mass o p π Invariant Mass o p π A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

13 p π + π System vs. Subsystems ) System (GeV/c Invariant Mass o p π + π COMPASS 9.4 π p p p π + p s. W ( % o 9) Invariant Mass o p π ) System (GeV/c Invariant Mass p p π + π COMPASS 9.4 π p p p π + p s. W ( % o 9) Invariant Mass o π + π ) System (GeV/c Invariant Mass o p π + π COMPASS 9.4 π p p p π + p s. W ( % o 9) Invariant Mass o p π + A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

14 Introducing Strangeness: p p p K + K p s A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

15 Invariant Mass o Subsystems COMPASS 9 + p p p K K p s W ( % o 9) φ() COMPASS 9 + p p p K K p s W ( % o 9) Invariant Mass o p K + K Invariant Mass o K K A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

16 Invariant Mass o Subsystems COMPASS 9 + p p p K K p s W ( % o 9) φ() COMPASS 9 + p p p K K p s W ( % o 9) Invariant Mass o p K + K Invariant Mass o K K. COMPASS 9 + p p p K K p s W ( % o 9) 5 4 Λ (5) COMPASS 9 + p p p K K p s W ( % o 9) Invariant Mass o p K Invariant Mass o p K A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS /9

17 Outlook Techniques or Partial Wave Analysis A. Austregesilo Baryon Spectroscopy at COMPASS 4/9

18 Analysis Technique Partial Wave Analysis Target proton remains intact Pomeron exchange dominates at high energies Isobar model Subsequent twobody decays Two dierent decay topologies Isobars: R ππ, R pπ +, R pπ Both mesons and baryons as intermediate states R ππ : (ππ) S, ρ (77), (98), (7),.. R pπ : ()P, N(44)P, N(65)S, (7)D,.. A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 5/9

19 Summary Conclusion Interesting data set including diractive dissociation o the beam proton Light baryon spectrum accessible in great detail Nπ, NK, ππ and KK decay modes PWA analysis ormalism developed A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 6/9

20 Summary Conclusion Interesting data set including diractive dissociation o the beam proton Light baryon spectrum accessible in great detail Nπ, NK, ππ and KK decay modes PWA analysis ormalism developed Outlook Adaptation o PWA sotware Acceptance correction with Monte Carlo Perorm PWA Determine poorly known parameters (widths, branching ratios,..) Identiy new decay modes (Nρ, Nφ,...) Gain insight into production mechanism A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 6/9

21 Summary Conclusion Interesting data set including diractive dissociation o the beam proton Light baryon spectrum accessible in great detail Nπ, NK, ππ and KK decay modes PWA analysis ormalism developed Outlook Adaptation o PWA sotware Acceptance correction with Monte Carlo Perorm PWA Determine poorly known parameters (widths, branching ratios,..) Identiy new decay modes (Nρ, Nφ,...) Gain insight into production mechanism Thank you. A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 6/9

22 p K + K System vs. Subsystems System K + K Invariant Mass o p System K + K Invariant Mass o p COMPASS 9 + p p p K K p s W ( % o 9) Invariant Mass o p K System COMPASS 9 + p p p K K p s W ( % o 9) Invariant Mass o K K System A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 7/9

23 Momentum Transer /c Events / 5MeV 5 4 COMPASS 8 p p p π + π p s /c Events / 5MeV COMPASS 8 + p p p K K p s Momentum Transer t (GeV/c ) Momentum Transer t (GeV/c ) p p p π + π p s p p p K + K p s A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 8/9

24 Feynman x F Distribution Events p s π + π COMPASS 9 p p p π + π p s W ( % o 9) p Events p s + K K COMPASS 9 + p p p K K W ( p s % o 9) p Feynman x Feynman x p p p π + π p s p p p K + K p s A. Austregesilo (aaust@tum.de) Baryon Spectroscopy at COMPASS 9/9