cesare bini, bernhard ketzer workshop on new partial wave analysis tools for next generation hadron...
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Cesare Bini, Bernhard Ketzer
Workshop on New Partial Wave Analysis Tools for Next Generation Hadron Spectroscopy Experiments
Camogli, Italy
22 June 2012
ATHOS 2012Discussion Session I
Discussion Session - Experiments
Conveners: Cesare Bini and Bernhard Ketzer
Recent results on pi-pi amplitudes at BES III (10’+5’)
B. Liu (Institute of High Energy Physics)
Search for exotics in three pion production at COMPASS (10’+5’)
S. Neubert (TU-Munchen)
Search for exotics in three pion production at CLAS (10’+5’)
P. Eugenio (Florida State University)
Discussion (45’)
State of the Art Lattice QCD
[J. Dudek, Phys. Rev. D 84, 074023 (2011)][J. Dudek at al., Hadron Spectrum Collaboration, Phys. Rev. D 82, 034508 (2010)]
negative parity
positive parity
exotic
Structure of states: study
with e.g.
C. Meyer
Comparison with Models
L-QCD Bag Flux tube Constituent gluon
S wave P wave
1−−,(0,1,2)−+
1++,(0,1,2)+−
1++,(0,1,2)+−
1−−,(0,1,2)−+
1+−,(0,1,2)++
JPC & Degeneracy pattern:
(0,1,1,1,2,2,3)+−
(0,1,2)++
(0,1,2)−+,1−−
(0,13,22,3)−−
(0,1,2)−+
1−−,(0,1,2)−+
(0,13,22,3)+−
(0,1,2)++
Model with a quasigluon in a P-wave with respect to the qq pair,
i.e. with successfully reproduces the L-QCD multiplets
Production Mechanisms
• Diffractive production: Regge- or Pomeron exchange
• pN annihilation: formation and production
• Photo-production
VES, E852, COMPASSCrystal Barrel
COMPASSCLAS
JPC=1−+ ‒ Pb vs H Target
[Alekseev et al., Phys. Rev. Lett. 104, 241803 (2010)]
[F. Haas, arXiv:1109.1789 (2011)]
Pb Pb p p 0 0 p p
S. Paul
S. Neubert
Nuclear Effect
Pb, Ni, H2 targets
M=1 enhanced for nuclei
1 1PCJ M 1 1PCJ M
S. Paul
S. Neubert
Photoproduction of JPC=1−+
Pion beam:
• JPC = 0−+ mainly S=0 hybrids: 1−−, 1++
mix with qq states
Photon beam:
• JPC = 1−−, VMD
mainly S=1 hybrids
exotic JPC , strength comparable to a2(1320)?
Flux tube model (Isgur 85, Close 95):
L-QCD (Dudek 09)
• strong photocoupling for cc hybrids
photoproduction more favorable for exotic hybrids?
Photoproduction of JPC=1−+
• no clear resonance signal• high-mass results fluctuate• accounts for 2% of total intensity at most• no evidence for 1−+ phase motion
P. Eugenio
Photoproduction of JPC=1−+
CLAS COMPASS
P. Eugenio
hp- vs h’p- Final States
• hp- waves scaled according to
phase space and BR to final state
• D, G waves very similar
• P wave very different in hp and h’p
Status of Analyses
• Isobar model analysis• isobar parameterizations: r, (pp)S
• rank of fit, full vs partial coherence• leakage, acceptance, resolution• t’ dependence• estimation of systematic error
• Signals for exotic mesons• diffraction, pbarp: rp, hp, h’p, f1p, b1p• photoproduction: none
Future
• Go beyond standard isobar model analysis:• where does the model fail?
study channels like
• include non-resonant production (dynamical effects, e.g. Deck)• analytic amplitudes • final state interactions• unitarity• understand a1
• multi-particle final states
Non-Resonant Production
Resonant production Non-resonant production
• Generate pure Deck-like events
[G. Ascoli et al., Phys. Rev. D 8, 3894 (1973)]
• Pass through Monte Carlo & PWA
• Normalize to 6−+0+ rp H wave
• Examine intensity in other waves
21
Duality and PWA FESR should work separately for Pomeron (background)
and classic Regge components and for fixed t and u.– At fixed u in π- π+ π- π+ one has zero Regge contribution
In π N elastic scattering one was able to use Regge exchange contributions as an approximation to high partial waves– This approach should be applicable to photon or meson
induced “top vertices” including reactions like π- Pomeron π- π- π+ with internal π exchange
This phenomenology suggests a PWA model that is combination of– Regge Born with low partial waves removed and – Parameterized low partial waves– FESR constraints on parameterized waves
G. Fox
Understand the a1
JPC = 1−+
• Higher masses accessible many disputed states: 0-+, 1++, 2-+,...
Multi-Particle (>3) Final States
Motivation:• Clarify the hybrid nature of the p1 branching ratios to different channels
Under investigation:
•
•
, 0,
0, , , ,
01 1, ,f f 1 1, ,f f
•
•
Model b1p f1p rp hp h’p h(1295)p Reference
Flux Tube, 3P0 170 60 5 - 20 0 - 10 0 – 10 [Isgur et al., Close et al.]
Flux Tube, IKP m=1.6 GeV/c2
24 5 9 2 [Isgur et al.]
Flux Tube, PSSm=1.6 GeV/c2
59 14 8 1 [Page et al.]
L-QCD 66 15 [McNeil and Michael]
Future
• Go beyond standard isobar model analysis:• multi-particle final states• coupled-channel analysis• final state interactions, unitarity• understand production mechanism: bins in t, s, polarization, probes• higher statistics, enlarge phase space• study model dependence• specify systematic errors
• Tools, etc.• common PWA framework across different experiments• plugin for amplitudes• validation of software• computing: fitting procedures, GPUs, etc.• access to data• teach young researchers
Conclusions
Hybrid mesons
are allowed in QCD, but are they realized in nature?
provide a test of flux tube formation confinement
can appear in exotic JPC quantum numbers smoking gun
High statistics data with p beam: COMPASS
exotic 1−+ waves in rp, h’p, f1p
non-resonant and resonant contributions
A dependence of M=1 production
Photoproduction: CLAS (also COMPASS)
no evidence for p1(1600) in charge transfer reaction
examine Pomeron production
Have we observed the lowest hybrid supermultiplet?
p1(1600), p(1800), p2(1880), ?
Many more interesting questions: Strangeness, Scalars, Glueballs, …
Partial Wave Analysis
Photoproduction Prim '( ') b tt e
'( ') ' btt t e
0.0015 < t’ < 0.01 GeV2/c2
t’ < 0.5·10-3 GeV2/c2
vanishes for t’→0
a2(1320) (M=1) present in both t’-ranges different production mechanisms?
Diffraction
Two clearly separated regions:
Phase difference a2(1320) - a1(1260): offset for two t’-regions!
Phase Difference a2-a1
Experiment Theory[G. Faeldt et al., Phys. Rev. C 79 014607 (2009)]
Plot by N. Kaiser, TUM
smooth transition between a2 photoproduction
to diffractive production with increasing t‘ possibility to cleanly separate photoproduction from diffraction
PWA in t’ bins for single mass bin 1.26 < m3p < 1.38 GeV/c2 (a2 region)
F(a1)F(a2)
(DF a2-a1)
determination of radiative width of a2(1320), p2(1670)