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 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


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


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


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 >


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 !


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.


Kyoto 9

Experimental approach to


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


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.


Kyoto 12

E325

J-PARC E16

Energy-Momentum dispersion of expected at J-PARC E16


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


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


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


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


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!


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


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


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


Kyoto 21

Documents

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