the p pp process in nuclei and the restoration of chiral symmetry
DESCRIPTION
The p pp process in nuclei and the restoration of chiral symmetry. CHAOS. Campaign of measurements of the p pp process in N and A The CHAOS spectrometer The A-dependence of p pp and comparison with theories The T-dependence of the p pp process - PowerPoint PPT PresentationTRANSCRIPT
The process in nuclei and the restoration of chiral symmetry
1. Campaign of measurements of the process in N and A
2. The CHAOS spectrometer
3. The A-dependence of and comparison with theories
4. The T-dependence of the process
5. Comparison with other experimental results
6. Conclusions
CHAOS : TRIUMF, Univ. of Colorado (USA), Univ. of Regina (Canada)
Univ. of Melbourne (Australia), Univ. of Sacramento (USA)
Univ. of Tubingen (Germany), Univ. of Trieste and INFN-Ts
The measurements with CHAOS
+,- p ++,- n @ T = 243, 264, 284 and 305 MeV
CHAOS : TRIUMF, Univ. of Colorado (USA), Univ. of Regina (Canada)
Univ. of Melbourne (Australia), Univ. of Sacramento (USA) Univ. of Tubingen (Germany), Univ. of Trieste and INFN-Ts
+ A + +,- X @ T=283 and A: 2H, 12C, 40Ca, 208Pb
+ 45Sc + +,- X @ T= 243, 264, 284 and 305 MeV
The CHAOS spectrometer
Trigger hardware &particle identification
Incoming -beam
283 MeV, + 2H + - p [p]
Magnet return yoke
Magnet dipole tip
Wire chambers
45Sc+,++,-N)44X Phase Space
The invariant mass distribution
Data from the CHAOS databaseF. Bonutti et al., NPA677(2000)213; P.Camerini et al., NPA735(2004)89.
TheoryH.C.Chiang et al., NPA644(1998)77;E.Oset et al., NPA678(2000)424.
2+,++,-N)N Phase Space
C=A
(M) /T N N
(M) /T A A
T: Total x-section(M): Diff. X-section
1. C is weakly related to the detector acceptanceA
2. The normalization of (M) to T removes the dependence of the number of scattering centers.
A A
3. The ratio of (M) to (M) is loosed
from the reaction mechanism C,
since the is a quasifree process.
A A
a) Cdescribes the clear effects of nuclear matter on the system focuses on the medium modifications of meson properties.
A
b) C, a useful observable for a direct comparison between the results from different experiments.
A
A
C; A-dependence of A
Oset: Full model of the process, standard nuclear effects accounted for, P-wave pionic modes included and the-meson dynamically generated.
Oset and Vicente,PRC60(1999)064621
A theoretical approach to
CHAOS vs Model● Limited acceptance (, Thr.) OK●
T and d/dOs OK
● T & A input parametrs OK
VicenteOsetChiang
Chiang
Pion production in nuclei, a quasifree process N N
Pion-pole: Contact term:
2- & 3-point: N N* ; .....
N N* ;
Standard nuclear effects are accounted for Fermi motion, Pauli blocking, Pion absorption,Quasi-free elastic scattering, …….
+ + + ….….
Role of Nuclear Matter on the (
I=J=system meson dynamically generated:
2m
Role of Nuclear Matter on 'sP-wave coupling of 's to p- & -h states:
N, h
A theoretical approach to in nucleiModel: Giessen, P. Muhlich et al., PLB595(2004)216
Model: Valencia, Nacher et al., NPA695(2001)295
Data: TAPS, Messcherdorp et al., PRL89(2002)222302
Model: Giessen, based on the Valencia’s elementary process, production/propagation of ’s in A via a semi-classical BUU transport model, careful treatment of FSI, no medium effects. Conclusions: “.. The downward shift in M, which TAPS was taken as an indication for chiral symmetry restoration, is reproduced solely by ordinary final state interactions of the two outgoing pions.”
BUT,• Giessen ~ Valencia in the I=0 channel;• Giessen < Velencia in the I=1 channel;• The same threshold strength for I=0 & I=1, where the thresh. enhancement is observed.
Theories should describe the I=0,1 (or 2) channels simultaneously !!!.
C; A-dependence of A
Oset: Full model of the process, standard nuclear effects discussed, P-wave pionic modes included and the-meson dynamically generated.
Oset and Vicente,PRC60(1999)064621
Muhlich: Model based on Oset’s developed for the and reactions, better treatment of FSI of pions with the nucleus, no medium modifications.
Muhlich et al.,PLB595(2004)216
TAPS CHAOS
I=0
I=1
E~420 MeV
~ 2/30
I~0
I=2
E~420 MeV
~ 1/30
C/P.S.; A-dependence of A
Davesne: S-wave pionic modes (LM model developed for =0.50 & tad-pole diagrams) and P-wave pionic modes (P-wave coupling of ’s to particle- and -hole configurations)
Hatsuda: meson generated by the fluctuations of the <qq> chiral order parameter. The existence of implies a strong threshold enhancement of M at c
phenomenon related to the (partial) restoration of the chiral symmetry.
Hatsuda et al., PRL 63(1999)2840
Davesne et al.,PRC62(2000)024604
Chiral Symmetry and in Hadron and Nuclear PhysicsHatsudaKunihiroJido
propagator: D(,)=[2 - m2 – ,)]-1
Effective mass .
=i
: One-loop selfenergy
spectral function: M = -1/ Im D(,) = -Im ,)
2–m2–Re,)]2+[Im,)]2
Partial Restoration of the Chiral Symmetry: m m(JP= 0+) (J
P= 0
-)
LM + tad-pole diagramsMm
m
. ~ 2mcritical
tree-level
4m
. 2
spe
ctra
l fu
ncti
on
GeV
1. critical ~ 0
2. Mild resonant behaviour at 2m
3. A ()I=J=0 resonant state is not required in the vacuum
C; T-dependence of A
Vicente-Oset: av ~ 1/3regardless of T
the reaction is localized at the nucleus surface
V-O, PRC60 (2004) 064621
M (Mev)
Experimental results: TAPS and CB VS CHAOS
CB CHAOS
I = 0
p= 40 8 MeV/c
~ 1/30
I ~ 0
p= 399 MeV/c
~ 1/30
CB: A.Starostin et al., PRL85(2000)5539
CHAOS: P.Camerini et al., PRC64(2001)067601
~ the same final result !
TAPS CHAOS
I=0
E~420 MeV
~ 2/30
I~0
E~420 MeV
~ 1/30
CHAOSTAPS
1. Threshold enhancement for C(Pb/C)
2. Density probed by TAPS: ~2*CHAOS
3. C(Pb/C) doesn’t reflect the higher
density inspected by TAPS Higher densities higher pion distortions
Data: TAPS, Messcherdorp et al., PRL89(2002)222302Data: CHAOS, F.Bonutti et al.,
NPA677(2000)213
S-wave pionic modes pole-position P-wave pionic modesFinal State Interactions
; (M) appears depleted in vacuum due to strong interference effects. Nuclear matter might modify pieces of the amplitude; therefore, canceling out the interference effects and restoring a space-phase like behavior at the 2mππ threshold.
Conclusions
The simultaneous study of the I=0 and I=1, 2 channels is essential to establish the correct size of the -strength.
experimental& theoretical
The interaction is modified by the medium when
strongly
weakly
I=0
I=1,2
In-medium modification of the correlation
partial restoration of the chiral symmetry C~
A N (M) /(M) A N
Cππ is a useful observable for probing medium modification of meson (hadron) properties A
hypothesis: