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Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment

Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment. Yoki Aramaki RIKEN. Contents Physics motivation Precedent & Our proposed plots etc. E16 spectrometer Preparation status Summary. Physics Motivation. Origin of hadron mass

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Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment

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  1. Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment Yoki Aramaki RIKEN Contents Physics motivation Precedent & Our proposed plots etc. E16 spectrometer Preparation status Summary

  2. Physics Motivation • Origin of hadron mass • Spontaneous breaking of chiral symmetry • Investigate chiral symmetry breaking • Theoretical prediction: In hot and/or dense matter, chiral symmetry is partially restored. • Probe: mass modification using low-mass vector meson YITP workshop on Hadron in Nucleus @ Kyoto

  3. Vector mesons • Di-electron decay channel • Small effect of final state interaction • Properties of r/w • A prediction: Large mass shift (ex. ~120 MeV@r = r0, Phys.Rev.C46(1992)R34, Phys.Rev.C52(1995)3364 ) • Relatively larger cross section than f • Properties of f • A prediction: Mass shift (20-30 MeV) • Narrow decay width (4.4 MeV) • No large resonances around the peak of f predictions of vector meson modification in medium Brown,Rho(1991), Hatsuda,Lee(1992), Klingle,Keiser,Weise(1997),etc. YITP workshop on Hadron in Nucleus @ Kyoto

  4. Measurement of r/w YITP workshop on Hadron in Nucleus @ Kyoto

  5. Precedent experiment (J-Lab CLAS g-7) • g+Ar+X@Eg 0.6-3.8GeV • Results • No mass shift for r • r Broadening due to the collisional process • (Low statistics for f) g+2H g+12C ω ω ρ ρ φ φ g+56Fe g+48Tl ω ρ φ BG subtracted (event mix-technique) R.Nesseripour et al.,Phys.Rev.Lett.99(2007)262302 YITP workshop on Hadron in Nucleus @ Kyoto

  6. Precedent experiment (KEK-PS E325) • p+Ar/w+X@12GeV • Results • The excess at low-mass side of w meson • The excess is coming from decay r mesons in the nucleus • r/w mass decrease by 9% • Different from CLAS-g7 • Need new experiment • Examine at J-PARC E16 • Mass distribution in nucleus • Basic information for quark condensates Linear dependence on density is assumed. m(r)/m(r0) = 1 – k(r/r0) , where r0: normal nuclear density, m(r): mass at density r, and k: parameter k = 0.092±0.002 from E325 YITP workshop on Hadron in Nucleus @ Kyoto

  7. New challenge for the r/w analysis < Mass distribution > • The overall mass distribution has essential information for quark condensates in nucleus. • cf. QCD sum rule • Uncertainties in low mass region • Shape and amplitude of h & w dalitz may affect a mass distribution of modified r meson • Determination of h & w dalitz • The prediction of Vector Meson Dominance (VMD) is used at KEK-PS E325 • Toward precise measurement • Determine the amplitudes and form factors for h and w dalitz by ourselves • Detect all decay products including gs from h and w dalitz YITP workshop on Hadron in Nucleus @ Kyoto

  8. New challenge for the r/w analysis < Form factor > • MAMI-A2 Collab., arXiv:1309.5648v1 • MAMI-A2: determine all decay products from he+e-g • SPS-NA60: determine only m+m- from hm+m-g • Form factor (FF) • determine the shape of e+e- from h&wdalitz decays • FF of he+e-g • The data is consistent with Vector Meson Dominance (VMD) • FF of we+e-p0 • CMD-2: consistent w/ VDM within LARGE error • NA60(wm+m-p0): NOT consistent w/ VDM • Might change the shape • We should measure this ! Phys.Lett.B613(2005)29 we+e-p0@CMD-2 Phys.Lett.B677(2009)260 YITP workshop on Hadron in Nucleus @ Kyoto

  9. Summary for challenge of r/w analysis • Amplitudedetermination w/ invariant mass method • The rough estimation of the yield (h & w dalitz decays) • The number of he+e-g (~1x104) • The number of we+e-p0 (~6x103) • cf. wm+m-p0@NA60 : 3x103 • Shapedetermination w/ the FF measurement • Form factor of he+e-g is consistent with VMD • Form factor of we+e-p0 should be measured by ourselves (We can obtain them as a byproduct by measuring the yield) • In order to reduce the uncertainty in r/w analysis, such further measurements in E16 are under discussion. YITP workshop on Hadron in Nucleus @ Kyoto

  10. Experimental approach to f YITP workshop on Hadron in Nucleus @ Kyoto

  11. Precedent experiment (KEK-PS E325) bg<1.25 (Slow) • p+Aφ+X@12GeV • Results & explanations • Excess at low mass side • Only slow moving φ in Cu target • Mass decrease by 3.4% • Questions • Nuclear size dep.? • Mom. (bg) Dep.? • Need new experiment • We proposed J-PARC E16 Cu Decays outside nucleus Blue line shows expected line shape including all experimental effects w/o mass modification e+e- invariant mass Decays inside nucleus R. Muto et al., PRL 98(2007) 042581 YITP workshop on Hadron in Nucleus @ Kyoto

  12. Nuclear size & bg dependences of fexpected in J-PARC E16 • Nuclear size dependence of the excess as a function of bg • E325 were used with C and Cu targets • Our targets are CH2, C, Cu, and Pb (we prepare 4 targets) • With high statistics, the expected calculations such as solid lines are constrained by our results. E325 J-PARC E16 YITP workshop on Hadron in Nucleus @ Kyoto

  13. Energy-Momentum dispersion of fexpected at J-PARC E16 • Energy-Momentum dispersion • Our observables: Energy & momentum of e+e- from f meson • Can observe the change from the dispersion in free space • Relation: (Ee+ + Ee-)2 = Mf2 + (Pe+ + Pe-)2 • The change of intercept(Mf2) is corresponding to the mass shift Dispersion in free space Mass shift s=5MeV is assumed YITP workshop on Hadron in Nucleus @ Kyoto

  14. The double-peak structure of fexpected at J-PARC E16 • Mass modification of f • The mass shift is 3.4% at E325 if the excess is interpreted as the shift of the peak position • Double-peak structure on invariant mass distribution • Observe f decayed inside and outside the nucleus • In addition to the mass dist. obtained w/ proton target (CH2), we can understand the mass distribution of f Cu Pb Proton E16 expectation (bg<0.5 & s=5MeV) YITP workshop on Hadron in Nucleus @ Kyoto

  15. J-PARC E16 experiment < The goal of J-PARC E16 > Not only examine results of E325 and CLAS-g7 but also perform the systematic studies using r, w, and f  Need high statistics & high resolution Intensity x10 Cross section x2 Acc. x5 Yield x100 • J-PARC E16 spectrometer • specialized to detect electron pairs • Coverage: • Horizontal: ±15 - ±135 (deg.) • Vertical : ±45 (deg.) • E16 will be performed at high momentum beam line YITP workshop on Hadron in Nucleus @ Kyoto

  16. High momentum beam line@J-PARC Hadron hall at J-PARC New beam line The construction of high-p beam line just started from this year YITP workshop on Hadron in Nucleus @ Kyoto

  17. Preparation status for J-PARC E16 spectrometer YITP workshop on Hadron in Nucleus @ Kyoto

  18. Preparation status for GEM tracker • GEM Tracker • 100, 200, and 300mm squares kapton(t=50mm) GEMs are used in E16 • 1st mass-production type GEM chamber of 100x100 mm2 has been tested w/ beam @LEPS and J-PARC • Position resolution of 100mm can be achieved (satisfied with our requirement) • Y.Komatsu et al, Nucl. Instrum. Meth. A, In press (2013) • Mass-production type of 200 and 300mm squares GEM chambers will be tested in this winter at ELPH • Preamp boards and support frames also continue at a good pace! Mass production type GEM chamber 300x300mm2 100x100mm2 200x200mm2 Mass production type of support frames is used with carbon-fiber-reinforced plastic,CFRP) YITP workshop on Hadron in Nucleus @ Kyoto

  19. Preparation status for HBD & LG • HBD • Kapton(t=50mm) triple- 300x300mm2 GEMs are operated in E16 • Pion rejection factor: >100 @electron eff. 70% w/ test beam • We are ready to move to the mass production phase • LG • All the lead-glass calorimeters are decomposed from TOPAZ barrels • Pion rejection factor: >20@ electron eff. 90% w/ test beam • We are also ready to move to the mass production phase YITP workshop on Hadron in Nucleus @ Kyoto

  20. Schedule for the first data taking • 2007: PAC stage-1 approval • 2008-2012: Detector R&D • 2013 Sep. : Started the mass production • GEM, Tracker readout board, and so on • 2014 Nov. – 2015 Jan.: Magnet construction • 2015 Feb. – Aug. : Detector installation in the magnet • 2016 Jan. – Mar. : Detector commissioning with beam YITP workshop on Hadron in Nucleus @ Kyoto

  21. Summary & Outlook • Summary • J-PARC E16 has been proposed • 100 times larger statistics than E325 • Investigate chiral symmetry restoration w/ high statistics • Systematic studies w/ f mesons (E325 x100) • Double peak structure, E-momentum dispersion, etc • Commissioning run starts on FY2015 • Outlook • Spectrometer • The mass production just started in this autumn • Analysis (for r/w analysis) • background study toward the measurement of h and wdalitz decay products YITP workshop on Hadron in Nucleus @ Kyoto

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