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