Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment Yoki Aramaki...
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Transcript of Experimental approach to the mass modification in nucleus by the J-PARC E16 experiment Yoki Aramaki...
Experimental approach to the mass modification in nucleus
by the J-PARC E16 experiment
Yoki AramakiRIKEN
Contents1.Physics motivation2.Precedent & Our proposed plots etc.3.E16 spectrometer4.Preparation status5.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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 2
Vector mesons
• Di-electron decay channel– Small effect of final state interaction
• Properties of – A prediction: Large mass shift (ex.
~120 MeV@ = 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 Nucleus @ Kyoto 3
predictions of vector meson predictions of vector meson modification in mediummodification in medium
Brown,Rho(1991), Hatsuda,Lee(1992),Klingle,Keiser,Weise(1997),etc.
Measurement of
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 4
Precedent experiment (J-Lab CLAS g-7)
• +A+X@E 0.6-3.8GeV• Results– No mass shift for– Broadening due to the
collisional process– (Low statistics for
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 5
+2H +12C
+56Fe+48Tl
φρ
ρ
ρφ
φ
ωω
ω
BG subtracted(event mix-technique)
R.Nesseripour et al.,Phys.Rev.Lett.99(2007)262302
Precedent experiment (KEK-PS E325)• p+A+X@12GeV • 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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 6
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 < Mass
distribution >
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 7
• 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 >
• 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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 8
MAMI-A2 Collab., arXiv:1309.5648v1•MAMI-A2: determine all decay products from e+e-•SPS-NA60: determine only +- from +-
e+e-0@CMD-2
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-1x104)• The number of e+e-0 (~6x103)
– cf. +-0@NA60 : 3x103
• 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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 9
Experimental approach to
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 10
Precedent experiment (KEK-PS E325)• p+Aφ+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. () Dep.?– Need new experiment
• We proposed J-PARC E16
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 11
R. Muto et al., PRL 98(2007) 042581
Cu
<1.25 (Slow)
e+e- invariant mass
Decays inside nucleus
Decays outside nucleus
Blue line shows expected line shape including all experimental effectsw/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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 12
E325
J-PARC E16
Energy-Momentum dispersion of expected at J-PARC E16
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 13
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: (Ee+ + Ee-)2 = M
2 + (Pe+ + Pe-)2
• The change of intercept(M2) is
corresponding to the mass shift
Dispersion in free space
The double-peak structure of expected at J-PARC E16
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 14
E16 expectation(<0.5 & =5MeV)
• Mass 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
PbCu
J-PARC E16 experiment
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 15
KEK- E325
J-PARC E16
Proton beam
109 / spill12GeV
1010 / spill30 GeV
Acceptance
(defined as) 1
5
Yield ~2000 ~ 2 x 105
• J-PARC E16 spectrometerspecialized to detect electron pairs
• Coverage:Horizontal: ±15 - ±135 (deg.)Vertical : ±45 (deg.)
• E16 will be performed at high momentum beam line
Intensity x10Cross section x2
Acc. x5
Yield x100
< The goal of J-PARC E16 >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 line@J-PARC
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 16
The construction of high-p beam line just started from this yearNew beam line
Hadron hall at J-PARC
Preparation status for J-PARC E16 spectrometer
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 17
Preparation status for GEM tracker• GEM Tracker
– 100, 200, and 300mm squares kapton(t=50m) 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 100m 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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 18
Mass production type of support frames is used with carbon-fiber-reinforced plastic, CFRP)
100x100mm2
200x200mm2
300x300mm2
Mass production type GEM chamber
Preparation status for HBD & LG• HBD– Kapton(t=50m) 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
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 19
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
Nov. 2, 2013YITP workshop on Hadron in Nucleus @
Kyoto 20
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, 2013YITP workshop on Hadron in Nucleus @
Kyoto 21