1 / 15

The p pp process in nuclei and the restoration of chiral symmetry

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

harrison-santiago
Download Presentation

The p pp process in nuclei and the restoration of chiral symmetry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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 • Comparison with other experimental results • 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

  2. The pp p measurements with CHAOS p+,- p p+p+,-n @ Tp = 243, 264, 284 and 305 MeV p+ A p+ p+,-X @ Tp=283 and A: 2H, 12C, 40Ca, 208Pb p+ 45Sc p+p+,- X @ Tp= 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

  3. The CHAOS spectrometer Trigger hardware & particle identification Incoming p-beam Magnet return yoke Wire chambers Magnet dipole tip 283 MeV, p+2H p+p- p [p]

  4. The pp invariant mass distribution 45Sc(p+,p+p+,-N)44X Phase Space 2H(p+,p+p+,-N)N Phase Space Theory H.C.Chiang et al., NPA644(1998)77; E.Oset et al., NPA678(2000)424. Data from the CHAOS database F. Bonutti et al., NPA677(2000)213; P.Camerini et al., NPA735(2004)89.

  5. s(Mpp) /sT A A Cpp= A A 1.Cpp is weakly related to the detector acceptance s(Mpp) /sT N N 2. The normalization of s(Mpp) to sT removes the dependence of the number of scattering centers. A A 3. The ratio of s(Mpp) to s(Mpp) is loosed from the reaction mechanism Cpp,, since the p pp is a quasifree process. A A sT: Total x-section s(Mpp): Diff. X-section A a) Cpp describes the clear effects of nuclear matter on the pp system focuses on the medium modifications of meson properties. A b) Cpp, a useful observable for a direct comparison between the results from different experiments. A

  6. Cpp; A-dependence of pp p A

  7. Cpp; A-dependence of pp p A Oset: Full model of the ppp process, standard nuclear effects accounted for, P-wave pionic modes included and the s-meson dynamically generated. Oset and Vicente, PRC60(1999)064621

  8. Vicente Oset Chiang Chiang Pion-pole: Contact term: .p N .p N 2- & 3-point: N N* D N N* D ; ; ..... p h N,D …. …. + + + p 2mp A theoretical approach to p -> pp CHAOS vs Model • Limited acceptance (W, Thr.) OK • sT and ds/dOs OK • T & A input parametrs OK Pion production in nuclei, a quasifree process pN ->ppN Standard nuclear effects are accounted for Fermi motion, Pauli blocking, Pion absorption, Quasi-free elastic scattering, ……. Role of Nuclear Matter on p's P-wave coupling of p's to p- & D-h states: Role of Nuclear Matter on the (pp)I=J=0 system s-meson dynamically generated:

  9. Model: Valencia, Nacher et al., NPA695(2001)295 Data: TAPS, Messcherdorp et al., PRL89(2002)222302 Model: Giessen, based on the Valencia’s g pp elementary process, production/propagation of pp’s in A via a semi-classical BUU transport model, careful treatment of FSI, no medium effects. A theoretical approach to g pp in nuclei Model: Giessen, P. Muhlich et al., PLB595(2004)216 • BUT, • Giessen ~ Valencia in the I=0 p0p0 channel; • Giessen < Velencia in the I=1 p0p+ 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 !!!. Conclusions: “.. The downward shift in Mpp, which TAPS was taken as an indication for chiral symmetry restoration, is reproduced solely by ordinary final state interactions of the two outgoing pions.”

  10. Cpp; A-dependence of pp p A TAPS CHAOS p0p0 I=0 p0p+ I=1 E~420 MeV r ~ 2/3r0 p+p- I~0 p+p+ I=2 E~420 MeV r ~ 1/3r0 Muhlich: Model based on Oset’s developed for the gp0p0and gp0p+,-reactions, better treatment of FSI of pions with the nucleus, no medium modifications. Oset and Vicente, PRC60(1999)064621 Oset: Full model of the p+p+p+,- process, standard nuclear effects discussed, P-wave pionic modes included and the s-meson dynamically generated. Muhlich et al., PLB595(2004)216

  11. Cpp/P.S.; A-dependence of pp p A Hatsuda et al., PRL 63(1999)2840 Hatsuda: s-meson generated by the fluctuations of the <qq> chiral order parameter. The existence of s implies a strong threshold enhancement of Msat rc~r0 phenomenon related to the (partial) restoration of the chiral symmetry. Davesne: S-wave pionic modes (LsM model developed for r=0.5r0 & tad-pole diagrams) and P-wave pionic modes (P-wave coupling of p’s to particle- and D-hole configurations) Davesne et al., PRC62(2000)024604

  12. . s, p s s propagator: Ds(w,r)=[w2 - m2s – Ss(w,r)]-1 Ss : One-loop selfenergy .r=0, Ss=ie Effective mass -Im Ss(w,r) sspectral function: Ms = -1/ p Im Ds(w,r) = Partial Restoration of the Chiral Symmetry:ms mp s(JP= 0+) p(JP= 0-) [w2–m2s–ReSs(w,r)]2+[ImSs(w,r)]2 p 4m2 .w2 1. rcritical ~ r0 2. Mild resonant behaviour at 2mp 3. A (pp)I=J=0 resonant state is not required in the vacuum Hatsuda Kunihiro Jido Chiral Symmetry and s in Hadron and Nuclear Physics LsM + tad-pole diagrams tree-level . w ~ 2mp  rcritical Ms(w ~2p) = -p [Im Ss(w,r)]-1  ~ Q(w-2mp)(1-)-1/2 . s spectral function GeV

  13. Vicente-Oset: rav ~ 1/3r0 regardless of T the reaction is localized at the nucleus surface Cpp; T-dependence of pp p A V-O, PRC60 (2004) 064621

  14. CB CHAOS • p0p0 I = 0 • pp= 40 8 MeV/c • r ~ 1/3r0 • p+p- I ~ 0 • pp= 399 MeV/c • r ~ 1/3r0 TAPS CHAOS TAPS p0p0 I=0 g p p E~420 MeV r ~ 2/3r0 p+p- I~0 p pp E~420 MeV r ~ 1/3r0 CHAOS Higherdensities higher pion distortions Mpp (Mev) Experimental results: TAPS and CB VS CHAOS CB: A.Starostin et al., PRL85(2000)5539 CHAOS: P.Camerini et al., PRC64(2001)067601 ~ the same final result ! 1. Threshold enhancement for Cpp(Pb/C) 2. Density probed by TAPS: ~2*rCHAOS 3. Cpp(Pb/C) doesn’t reflect the higher density inspected by TAPS Data: TAPS, Messcherdorp et al., PRL89(2002)222302 Data: CHAOS, F.Bonutti et al., NPA677(2000)213

  15. Conclusions strongly weakly I=0 I=1,2 Cππ is a useful observable for probing medium modification of meson (hadron) properties A The pp interactionis modified by the medium when In-medium modification of the pp correlation partial restoration of the chiral symmetry s Cpp~ A s(Mpp) /s(Mpp) A N experimental& theoretical The simultaneous study of the pp I=0 and I=1, 2 channels is essential to establish the correct size of the s-strength. s S-wave pionic modes pole-position P-wave pionic modes Final State Interactions ; s(Mpp) 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. N hypothesis:

More Related