Hiroyuki Kamano (RCNP, Osaka Univ.)

transcript

Dynamical coupled-channels approach to meson production reactions in the N* region and its application to neutrino-nucleon/nucleus

reactions

Hiroyuki Kamano(RCNP, Osaka Univ.)

Seminar at J-PARC, March 19, 2012

Since the late 90s, huge amount of high precision data of meson photo-production reactions on the nucleon target has been reported from electron/photon beam facilities.

JLab, MAMI, ELSA, GRAAL, LEPS/SPring-8, …

Experimental developments

E. Pasyuk’s talk at Hall-B/EBAC meeting

Opens a great opportunity to make quantitative study of the N* states !!

Objectives and goals:

Through the comprehensive analysis of world data of pN, gN, N(e,e’) reactions,

Determine N* spectrum (pole masses)

Extract N* form factors

(e.g., N-N* e.m. transition form factors)

Provide reaction mechanism information necessary for interpreting N* spectrum, structures and dynamical origins

Dynamical coupled-channels analysis ofmeson production reactions

Spectrum, structure,…of N* states

Lattice QCDHadron Models

Analysis Based on Reaction Theory

Reaction Data

H. Kamano (RCNP), T.-S. H. Lee (ANL), S. Nakamura (JLab), T. Sato (Osaka U./KEK)B. Julia-Diaz (Barcelona U.), A. Matsuyama (Shizuoka U.), N. Suzuki (Osaka U.)

A. Matsuyama, T. Sato, T.-S.H. Lee Phys. Rep. 439 (2007) 193

Dynamical coupled-channels model of meson production reactions

Singular!

Dynamical coupled-channels model for meson production reactions

Meson production dataN* spectrum, structure, …

Reaction dynamics

Hadronic amplitudes in the DCC model

Non-resonant amp. Rsonant amp.

B B’

M M’

Amplitudes of two-body meson-baryon reactions

For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)

Reaction channels:

Hadronic amplitudes in the DCC modelFor details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)

B B’

M M’

M’’

B’’p, r, s, w,..

N N, D

s-channel u-channel

t-channel contact

Exchangepotentials

“Z-diagrams”

~ 150 Feynman diagrams

Meson-Baryon Green functions

Stable channels

Quasi 2-body channelsp

Produce 2-body and 3-body ppN cuts required by the unitarity !!

B B’

M M’

M’’

B’’

B B’

M M’

Dressed N*-MB vertex

Meson cloudBare vertexBare

propagator(Bare mass)

Self energy

Dressed N* propagatorNon-resonant amp.

Effects of rescattering processes (reaction dynamics) are included consistently with the unitarity of S-matrix.

Electromagnetic amplitudes in the DCC model

B B’

E.M. current interactions are treated perturbatively.

For details see Matsuyama, Sato, Lee, Phys. Rep. 439,193 (2007)

+=Dressed gN N* vertex

Bare vertex

Rescattering effect

DCC analysis of meson production reactions (current status)

p-p hn

pp KL, KS

gp KL, KS

2006 ~ 2009

5 channels (pN,hN,pD,rN,sN)

< 2 GeV

< 1.6 GeV

< 2 GeV

2010 ~ 2012

7 channels (pN,hN,pD,rN,sN,KL,KS)

< 2.1 GeV

< 2 GeV

< 2.2 GeV

# of coupled channels

Fully combined analysis of gN , pN pN , hN , KL, KS reactions !!

Kamano, Nakamura, Lee, Sato(2012)

Analysis Database

Pion-inducedreactions (purely strong reactions)

Photo-productionreactions

~ 28,000 data points to fit

Partial wave amplitudes of pi N scattering

Kamano, Nakamura, Lee, Sato2012

Previous model (fitted to pN pN data only)[PRC76 065201 (2007)]

Real part

Imaginary part

Pion-nucleon elastic scattering

Target polarization

1234 MeV

1449 MeV

1678 MeV

1900 MeV

Angular distribution

Kamano, Nakamura, Lee, Sato, 2012

pi N MB reactionsKamano, Nakamura, Lee, Sato, 2012

1732 MeV

1845 MeV

1985 MeV

2031 MeV

1757 MeV

1879 MeV

1966 MeV

2059 MeV

1792 MeV

1879 MeV

1966 MeV

2059 MeV

Data handled with the help of R. Arndt

pi N pi pi N reaction

Parameters used in the calculation are from pN pN analysis.

Kamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC79 025206 (2009)

Full result

Phase spaceFull result

W (GeV)

C. C. effect off

Single pion photoproduction

Kamano, Nakamura, Lee, Sato, 2012 Previous model (fitted to gN pN data up to 1.6 GeV) [PRC77 045205 (2008)]

Angular distribution Photon asymmetry

1137 MeV 1232 MeV 1334 MeV

1462 MeV 1527 MeV 1617 MeV

1729 MeV 1834 MeV 1958 MeV

Kamano, Nakamura, Lee, Sato, 2012

1137 MeV 1232 MeV 1334 MeV

1462 MeV 1527 MeV 1617 MeV

1729 MeV 1834 MeV 1958 MeV

Kamano, Nakamura, Lee, Sato 2012

Double pion photoproductionKamano, Julia-Diaz, Lee, Matsuyama, Sato, PRC80 065203 (2009)

Parameters used in the calculation are from pN pN & gN pN analyses.

Good description near threshold

Reasonable shape of invariant mass distributions

Above 1.5 GeV, the total cross sections of pp0p0 and pp+p-

overestimate the data.

Single pion electroproduction (Q2 > 0)

Fit to the structure function data (~ 20000) from CLAS

Julia-Diaz, Kamano, Lee, Matsuyama, Sato, Suzuki, PRC80 025207 (2009)

p (e,e’ p0) p

W < 1.6 GeVQ2 < 1.5 (GeV/c)2

is determinedat each Q2.

g (q2 = -Q2)q

N-N* e.m. transitionform factor

Meson cloud effect in gamma N N* form factors

GM(Q2) for g N D (1232) transition

Note:Most of the available static hadron models give GM(Q2) close to “Bare” form factor.

How to extend the DCC model to neutrino reactions

B B’

Just replace E.M. current by vector and axial currents.

+=Dressed gN N* vertex

Bare vertex

Rescattering effect

V, A V, A

Dressed VN or AN N* vertex

V, A V, A

V, A V, A V, A

How to extend the DCC model to neutrino reactions

Vector part Axial part

What we need to do:

Ready for neutrino reaction(We can get all isospin components simply by isospin rotation.)

Evaluation ofg neutron N* verticesfor I = ½ N* states

For N*s except D(1232), as a first step, we evaluateA N N* vertices frompNN* couplings by making use of PCAC.

Construct AN MB potentialfor MB = pD, rN, sN, KL, KS(We already have the potentialfor MB = pN case.)

Hiroyuki Kamano (RCNP, Osaka Univ.)

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