Motivation for studies of pion Motivation for studies of pion induced dilepton production induced dilepton production Motivation for pion experiments (perspective from 2001): • Subthreshold / production amplitudes in NVN a)Key measurement for in-medium /mass modification? b) unique tool to study Vector Meson coupling to baryon resonances • Vector mesons production off nucleus
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Motivation for studies of pion induced dilepton production
Motivation for studies of pion induced dilepton production. Motivation for pion experiments (perspective from 2001): Subthreshold / production amplitudes in N V N a)Key measurement for in-medium / mass modification? b) unique tool to study Vector Meson coupling to baryon resonances - PowerPoint PPT Presentation
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Motivation for studies of pion induced Motivation for studies of pion induced dilepton productiondilepton production
Motivation for pion experiments (perspective from 2001):
•Subthreshold / production amplitudes in NVN a)Key measurement for in-medium / mass modification?
b) unique tool to study Vector Meson coupling to baryon resonances
dominant role of baryons (also for SPS) ! dominant role of baryons (also for SPS) ! important for future CBM important for future CBM
2222 )]([)](Re[
)(2)(
MImMmM
MImMA
even at high T int. with baryons is dominant !
•Direct -N Interactions (‘Rhosobars’)
In medium vector meson properties and N scattering
..)4)( VN
N
V
VT
m
mVN
T forward scattering amplitude
)0(12),()(2
)(
VNCM
CMV
Vnp ImTsq
qMs
•low density theorem
•Optical and detailed balance theorem
B.Friman N.PhysA610(1996)
R. Rapp and J.Wambach
In medium properties are related to elementary TVN !
Resonance contribution at vector mass region- off shell contributions?URQMD: arXiv:0811.4073v2: resonance model HSD : arXiv:0712.0635v2
Resonance contribution at vector mass region- off shell contributions?
• data seems to favour smaller VM contribution at the pole
p-n puzzle? pp vs “quasi-free” pn @ 1.25
Model Calculations:a) NN-bremsstrahlung Kaptari & Kämpfer (K&K)
b) , yield constraint by data. Dalitz decay Krivoruchenko et al. Phys. Rev. D 65 (2001) 017502 + VMD form-factor (Q. Wan and F. Iachello, Int. J. Mod. Phys. A 20 (2005) 1846)
• pn data are not (yet) described by calculations !off –shell contribution with strong isospin depend.?
Vector meson production in πN
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I=1/2 (N*) I=3/2()
1. π- + p n e+e- reactions in Isospin space
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+ n : exit channel + n : exit channel
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I=1 isovector I=1 isoscalar
TVN π- + n
= TI=0() +TI=1() • different resonance probed via /
2. π+ + n : π- + p rotated in Isospin space around Y by 1800
TVN π+ +n
= TI=0() - TI=1() • opposite sign of iso-vector part (-1)I
• access to vector-meson Baryon interaction !
Meson and resonanse Meson and resonanse production with pion beamsproduction with pion beams
Eth
resh
[GeV
]
Mx [GeV/c2]
/
pp->ppX
-p->Xn
Meson production thresholds
/
• direct resonance excitation: second, third res. region • strong off-shell contribution for production D13(1520) partial wave analysis of Nππ channel. What about ? D. M. Manley et al.Phys. Rev. D 30(1984) 904
• p>0.5 GeV/c weak contribution from (1232) (1232)->Ne+e- small !!
N,
M. Effenberger et al. PHYS. REV. C 60(1999) 044614
p~1.3 GeV/c
1.21 1.52 1.68
s
2
224
2*2 |
)()(|
||||
mimmm
Tf
mimmm
Tf
mee
enep npnp
VDM model: f/ decay couplings
2011.06.0
2036.07.6
GeVfkeVee
GeVfkeVee
Relative phase of Tp->()N determines interference pattern
/ production in --n n reactionsreactions
Exclusive: --p ->ep ->e++ee- - nn
++n ->en ->e++ee- - p (via p (via +++d)? +d)?
T/ amplitudes in N (/) N reactions
• Coupled channels calculations(N, N, N, ,…)
- opposite sign of T/ :
destructive interferences in π- p and positive in +n
• Large influence of I=1/2 below threshold: S11(1535) and D13(1520)
TV
N
- p (/) n +n (/) p M.F.M. Lutz , B. Froman, M. Sayuer . / Nuclear Physics A 713 (2003) 97–118
/ interference yield in --n (published-n (published-2003)2003)
--n n e e++ee- - n n ++p p ee++ee- - p p M.F.M. Lutz , B. Friman, M. Sayuer Nuclear Physics A 713 (2003) 97–118
/ interference: different models M.F.M. Lutz , B. Friman, M. Sayuer Nuclear Physics A 713 (2003) 97–118
B. Kaempfer , A Titov , R.Reznik Nucl. Phys. A721(2003)583
A.Titov, B.KaempferEPJA 12(2001)217
• quantitatively same picture but differs in details:
resonance contributions(i.e D15(1520) not important)
coupling strengths (quark model vs coupled chann.)
• Virtual photon angular distributions in CM sensitive to res.contributions
• no mass shift • in-medium broadenning: transparency measurement
~ absorption =vabs 90 MeV !
() =217 14
pe+e- >0.8 GeV/c
arXiv:0707.2324v3
0
CLAS
Theory’2008: Sensitivity to an in-medium mass shift
E= 1500 – 2200 MeV
for E= 1500 – 2200 MeV effect only observable for extremely hard cut on ω momentum:
E= 900 – 1200 MeV
• possible mass shift observable near threshold even without cut on ω momentum c/MeV150p
Gi-BUU simulations: K. Gallmeister et al. Prog. Part. Nucl. Phys. 61 (2008) 283
3 scenarios:1.) no in-medium modification2.) broadening3.) broadening and mass shift
Any chance for HADES?Any chance for HADES?HADES proposal 2006HSD: calculations (E. Bratkovskaya, D. Mishra)
experiment exp. rates:
25 day at 1.3 GeV/c and maximal luminosity
p+Nb @ 3.5 GeV/c rates:
expected 40/daymeasured 10/day
1.17 GeV
3.5 GeV
Vector mesons / at SIS
p+p at 3.5 GeV
PRELIMINARY
2005
40Ar+ 38KCl 1.75 AGeVp+ 92Nb 3.5 GeV
20072008“on-line spectrum!”
• Data are available! • No quick answer to the question on in-medium / spectral function ! • Only comprehensive analysis (in progress) of the pp/p+A/and A+A can give answer
resonance contribution?
Conclusions (to be work-out during this meeting)
• π- p (π+ n ) reactions below threshold – sensitive tool to study baryon-vector meson dynamics :
1. relevant for in-medium properties (SIS/18/300->SPS)
2. separation of vector/isovector em.current (intereference pattern)
• πA reactions –probe for in-medium vector meson properties and low momentum
+ see other contributions (Madaleine , Laura, Elena, Gyuri,…)