Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment Yoki Aramaki RIKEN Contents 1.Physics motivation 2.Precedent & Our proposed plots etc. 3.E16 spectrometer 4.Preparation status 5.Summary

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 Nov. 2, 2013 YITP workshop on Hadron in Kyoto1

Vector mesons Di-electron decay channel – Small effect of final state interaction Properties of  – A prediction: Large mass shift (ex. ~120  =  0, Phys.Rev.C46(1992)R34, Phys.Rev.C52(1995)3364 ) – Relatively larger cross section than  Properties of  – A prediction: Mass shift (20-30 MeV) – Narrow decay width (4.4 MeV) – No large resonances around the peak of  Nov. 2, 2013 YITP workshop on Hadron in Kyoto2 predictions of vector meson modification in medium Brown,Rho(1991), Hatsuda,Lee(1992), Klingle,Keiser,Weise(1997),etc.

Measurement of  Nov. 2, 2013 YITP workshop on Hadron in Kyoto3

Precedent experiment (J-Lab CLAS g-7)  +A    GeV Results – No mass shift for  –  Broadening due to the collisional process –(Low statistics for  Nov. 2, 2013 YITP workshop on Hadron in Kyoto4 +2H+2H  + 12 C  + 56 Fe  + 48 Tl φ ρ ρ ρ φ φ ω ω ω BG subtracted (event mix-technique) R.Nesseripour et al.,Phys.Rev.Lett.99(2007)262302

Precedent experiment (KEK-PS E325) p+A   Results – The excess at low-mass side of  meson The excess is coming from decay  mesons in the nucleus –  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 Nov. 2, 2013 YITP workshop on Hadron in Kyoto5 Linear dependence on density is assumed. m(  )/m(  0 ) = 1 –  (  0 ), where  0 : normal nuclear density, m(  ): mass at density , and  : parameter  = 0.092±0.002 from E325

New challenge for the  analysis Nov. 2, 2013 YITP workshop on Hadron in Kyoto6 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  &  dalitz may affect a mass distribution of modified  meson Determination of  &  dalitz – The prediction of Vector Meson Dominance (VMD) is used at KEK-PS E325 Toward precise measurement – Determine the amplitudes and form factors for  and  dalitz by ourselves – Detect all decay products including  s from  and  dalitz

New challenge for the  analysis Form factor (FF) – determine the shape of e+e- from  &  dalitz decays FF of   e+e-  – The data is consistent with Vector Meson Dominance (VMD) FF of   e+e-  0 – CMD-2: consistent w/ VDM within LARGE error – NA60(    +  -  0 ): NOT consistent w/ VDM – Might change the shape We should measure this ! Nov. 2, 2013 YITP workshop on Hadron in Kyoto7 MAMI-A2 Collab., arXiv: v1 MAMI-A2: determine all decay products from   e+e-  SPS-NA60: determine only  +  - from    +  -    e+e-  Phys.Lett.B613(2005)29 Phys.Lett.B677(2009)260

Summary for challenge of  /  analysis Amplitude determination w/ invariant mass method – The rough estimation of the yield (  &  dalitz decays) The number of   e+e-  1x10 4 ) The number of   e+e-  0 (~6x10 3 ) – cf.    +  -  : 3x10 3 Shape determination w/ the FF measurement – Form factor of   e+e-  is consistent with VMD – Form factor of   e+e-  0 should be measured by ourselves (We can obtain them as a byproduct by measuring the yield) In order to reduce the uncertainty in  /  analysis, such further measurements in E16 are under discussion. Nov. 2, 2013 YITP workshop on Hadron in Kyoto8

Experimental approach to  Nov. 2, 2013 YITP workshop on Hadron in Kyoto9

Precedent experiment (KEK-PS E325) p+A  Results & explanations – Excess at low mass side Only slow moving φ in Cu target – Mass decrease by 3.4% Questions – Nuclear size dep.? – Mom. (  ) Dep.? – Need new experiment We proposed J-PARC E16 Nov. 2, 2013 YITP workshop on Hadron in Kyoto10 R. Muto et al., PRL 98(2007) Cu  <1.25 (Slow) e + e - invariant mass Decays inside nucleus Decays outside nucleus Blue line shows expected line shape including all experimental effects w/o mass modification

Nuclear size &  dependences of  expected in J-PARC E16 Nuclear size dependence of the excess as a function of  – 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. Nov. 2, 2013 YITP workshop on Hadron in Kyoto11 E325 J-PARC E16

Energy-Momentum dispersion of  expected at J-PARC E16 Nov. 2, 2013 YITP workshop on Hadron in Kyoto12 Mass shift  =5MeV is assumed Energy-Momentum dispersion – Our observables: Energy & momentum of e+e- from  meson – Can observe the change from the dispersion in free space Relation: (E e+ + E e- ) 2 = M  2 + (P e+ + P e- ) 2 The change of intercept(M  2 ) is corresponding to the mass shift Dispersion in free space

The double-peak structure of  expected at J-PARC E16 Nov. 2, 2013 YITP workshop on Hadron in Kyoto13 E16 expectation (  <0.5 &  =5MeV) M ass modification of  – 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  decayed inside and outside the nucleus – In addition to the mass dist. obtained w/ proton target (CH2), we can understand the mass distribution of  Proton Pb Cu

J-PARC E16 experiment Nov. 2, 2013 YITP workshop on Hadron in Kyoto14 KEK- E325 J-PARC E16 Proton beam 10 9 / spill 12GeV / spill 30 GeV Acceptan ce (defined as) 1 5  Yield ~2000~ 2 x 10 5 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 Intensity x10 Cross section x2 Acc. x5 Yield x100 Not only examine results of E325 and CLAS-g7 but also perform the systematic studies using , , and   Need high statistics & high resolution

High momentum beam Nov. 2, 2013 YITP workshop on Hadron in Kyoto15 The construction of high-p beam line just started from this year New beam line Hadron hall at J-PARC

Preparation status for J-PARC E16 spectrometer Nov. 2, 2013 YITP workshop on Hadron in Kyoto16

Preparation status for GEM tracker GEM Tracker – 100, 200, and 300mm squares kapton(t=50  m) GEMs are used in E16 – 1 st mass-production type GEM chamber of 100x100 mm 2 has been tested w/ and J-PARC Position resolution of 100  m 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! Nov. 2, 2013 YITP workshop on Hadron in Kyoto17 Mass production type of support frames is used with carbon-fiber-reinforced plastic, CFRP) 100x100mm 2 200x200mm 2 300x300mm 2 Mass production type GEM chamber

Preparation status for HBD & LG HBD – Kapton(t=50  m) triple- 300x300mm 2 GEMs are operated in E16 – Pion rejection factor: 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: electron eff. 90% w/ test beam – We are also ready to move to the mass production phase Nov. 2, 2013 YITP workshop on Hadron in Kyoto18

Schedule for the first data taking 2007: PAC stage-1 approval : 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 Nov. 2, 2013 YITP workshop on Hadron in Kyoto19

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/  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  analysis) background study toward the measurement of  and  dalitz decay products Nov. 2, 2013 YITP workshop on Hadron in Kyoto20