Dec. 1, 2005 S. Sawada / J-PARC-HS05 1

Dimuon measurement at J-PARC(LoI-15: Physics of high-mass dimuon production at the 50-GeV Proton Synchrotron)

Shin’ya Sawada (KEK)

CollaborationAbilene Christian UniversityArgonne National Laboratory

Duke UniversityHigh Energy Accelerator Research Organization (KEK)

University of Illinois at Urbana-ChampaignKyoto University

Los Alamos National LaboratoryMassachusetts Institute of Technology

Tokyo Institute of Technology

Dec. 1, 2005 S. Sawada / J-PARC-HS05 2

Contents

Physics Goals– Flavor asymmetry (d-bar/u-bar) at large xBj

– Antiquark distribution in nuclei– Quark energy loss in nuclei

– d-bar/u-bar via J/ production

– Drell-Yan and J/ with polarized target/polarized beam Dimuon Spectrometer High Momentum Beamline To do (toward proposal submission)

– Firm collaboration!– Real work including MC simulation of the detectors etc.– Physics with polarized beams?

Dec. 1, 2005 S. Sawada / J-PARC-HS05 3

Dimuon Spectrum from Fermilab Experiments

A series of experiments: E605/772/789/866– 800 GeV/c p + p/d/A +-X

Two components in the +- spectrum.– Continuum: Drell-Yan process– Vector mesons: J/,

• Closed geometry

•Vertical bending

Dec. 1, 2005 S. Sawada / J-PARC-HS05 4

d-bar/u-bar Asymmetry Measurement

Ratio of p+d cross section to p+p d-bar/u-bar

Drell-Yan:

J/Psi, Upsilon (800 GeV):

pd

2 ppx1 x2

1

21

d (x)

u (x)

)(

)(1

2

1

221

xg

xg

p

n

xx

pp

pd

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dbar/ubar at Large x using 50 GeV Protons

DY cross section is ~16 times larger at 50 GeV than at 800 GeV.

2121

, fixedat 1

xxsdxdx

d DY

J-PARC can measure d-bar/u-bar at larger x.

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d-bar/u-bar Asymmetry and the Origins of the Nucleon Sea

d-bar/u-bar asymmetry suggests that there are two origins of the antiquarks in the nucleon, one from the perturbative g q qbar and the other from the meson cloud.

d-bar/u-bar measurement probes parton structure at peripheral regions of the nucleon.

From ACU web.

Dec. 1, 2005 S. Sawada / J-PARC-HS05 7

Modification of Parton Distributions in Nuclei

EMC effect observed in DIS

How is the antiquark distribution modified in nuclei?

(p+A)/(p+d)

Sensitive to u-bar distribution in nuclei.

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Quark Bremsstrahlung in Nuclear Medium

Landau-Pomeranchuk-Migdal (LPM) effect of medium modification for electron brems has been observed at SLAC

LPM effect in QCD remains to be identified.

– DIS: dE/dx ~ 0.5 GeV/fm (PRL 89 (2002) 162301)

– DY: dE/dx ~ 2.5 +- 0.6 GeV/fm (PRL 86 (2001) 4483)

Quark energy loss dE/dx is predicted to be proportional to L2.

Enhanced quark energy loss in traversing quark-gluon plasma.

Quark energy loss in cold nuclei needs to be better measured!

Dec. 1, 2005 S. Sawada / J-PARC-HS05 9

Quark Energy Loss with DY at 50 GeV

At 50 GeV, energy loss can be well measured.– Fractional energy loss is larger at 50 GeV. Effect is amplified.

Possible to test the L dependence of the LPM effect from the A dependence.

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J/Psi Production at 50 GeV

At 800 GeV, J/Psi production is dominated by gluon-gluon fusion process.

At 50 GeV, J/Psi production is dominated by quark-antiquark annihilation process.

J/Psi production at 50 (and 30) GeV is sensitive to quark and antiquark distributions.

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dbar/ubar asymmetry via J/Psi at 50 GeV

Ratio of p+dJ/Psi over p+pJ/Psi is sensitive to dbar/ubar.

At 30 GeV, J/Psi production could also be well measured.

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Polarized Drell-Yan / J/

Single spin asymmetry Xiandong Ji ALL: sea quark polaization

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Spectrometer

Two vertically bending magnets with pT kick of 2.47 GeV/c and 0.5 GeV/c.

“Closed geometry”– A tapered copper beam dum

p and Cu/C absorbers placed within the first magnet.

Tracking is provided by three stations of MWPC and drift chambers.

Muon id and tracking are provided.

2x1012 50 GeV p/spill.

tan(/2) ~ 1 / f, :opening angle of two muons.

Based on the Fermilab spectrometer for 800 GeV, the length can be reduced but the aperture has to be increased.

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Simulation of Detector Acceptance

Expected Drell-Yan counts for a two-month p+d run at 50 GeV.– 2x1012 protons/spill– 50-cm long liquid deuteriu

m target– Assume 50 percent overall

efficiency

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Simulation of Detector Resolutions

Expected resolutions for Drell-Yan events.

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Possible Layout of Hadron Hall

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High Momentum Beam Line

Primary beams: proton, polarized proton and heavy ions (future). Secondary beams: proton, pion, kaon, anti-proton, etc.

The radiation shielding of the SY tunnel is designed so that 2% (15kW) loss allowed at SM1.

Exp. setup could be staged.

~120m

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Beam Line Configuration & Optics I

Secondary Beams:– Use a thin (2% = 15kW loss) target at SM1

– Collect them at forward angles

– Transfer them for ~120m Schematic Layout around SM1:

Shielding of the switching yard has been designed to accommodate the loss at SM1

Dec. 1, 2005 S. Sawada / J-PARC-HS05 19

Beam Line Configuration & Optics II

Beam Optics: a preliminary design has been studied.– Example: 10 GeV/c particles

• Bore radius of the quadrupole magnets is 10 cm or less.– 0.2 msr% can be achieved.

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Beam Line Configuration & Optics III

Primary Beams: – Beam line configuration is almost the same as the case for the secon

dary beams except for equipments at SM1. – In order to cut a fraction (10 to 100 ppm) of the primary beam, a bea

m stealer can be used.• 1014 primary protons 109-1010 protons

Field free hole

Dec. 1, 2005 S. Sawada / J-PARC-HS05 21

Beam Line Configuration & Optics IV

– In order to get a few % of the primary beam, an electrostatic septum will be used.

• 1014 primary protons ~1012 protons

• High heat and radiation deposit have to be taken into account.

• More R&D works should be necessary to estimate the beam loss and to finalize the design.

• Crystal channeling is a possibility: test experiment to be performed.

– In order to get 100 % of the primary beam, a conventional bending magnet can be used.

• Weak primary beam (at the beginning of the accelerator operation, and heavy ion beam or polarized beam in the future).

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Yield Estimation (30GeV)

30GeV protons + 2% loss copper target. Production angle of 4 degree and (p/p) = 0.2msr%.

Momentum(GeV/c)

d/dpd(mb/sr/GeV/c)

Yield at SM1

(per 1014 protons)

Yield at 120m

(per 1014 protons)

+ 5 1400 3.7E7 2.4E7

+ 10 210 1.1E7 8.9E6

- 5 1000 2.6E7 1.7E7

- 10 130 6.7E6 5.4E6

K+ 5 130 3.3E6 1.3E5

K+ 10 28 1.4E6 2.8E5

K- 5 61 1.6E6 6.4E4

K- 10 7.0 3.6E5 7.2E4

pbar 5 11 2.8E5 2.8E5

pbar 10 1.1 5.7E4 5.7E4

Even with 30 GeV protons, enough intensity can be obtained especially for pions!

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Yield Estimation (50GeV)

50GeV protons + 2% loss copper target. Production angle of 4 degree and (p/p) = 0.2msr%.

Momentum(GeV/c)

d/dpd(mb/sr/GeV/c)

Yield at SM1

(per 1014 protons)

Yield at 120m

(per 1014 protons)

+ 5 3700 9.5E7 6.2E7

+ 10 930 4.7E7 3.8E7

- 5 3700 9.5E7 6.2E7

- 10 700 3.6E7 2.9E7

K+ 5 440 1.1E7 4.4E5

K+ 10 120 6.2E6 1.2E6

K- 5 220 5.7E6 2.3E5

K- 10 56 2.9E6 5.8E5

pbar 5 53 1.4E6 1.4E6

pbar 10 16 8.4E5 8.4E5

To get more intensity for higher momentum beams, extraction at more forward angles can be considered.

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Cost & Schedule: Magnets from the World

Total cost if constructed from scratch: $5-8M?? We have no budget so far to construct a high m

omentum beam line. But we are doing every effort to construct it with as small cost as possible, e.g. reuse of second-hand magnets…

Already from SLAC, Saclay, CERN, … Large dipole magnets from ANL (previously used

for the polarized beam line at FNAL) are under process!

The high momentum beam line can be constructed by using some of these second-hand magnets.

The high momentum beam line can be constructed even at the beginning of the NP hall operation from the viewpoint of the facility design.

Large dipole magnets at the Meson Pol beam line (FNAL)

Dec. 1, 2005 S. Sawada / J-PARC-HS05 25

To Do

Proposal:– Proposals for day-1 and early stage of Phase 1 are to be

called soon.– The first deadline of proposal submission is April 28.– We should prepare a proposal.

Detailed study on the spectrometer has to be done.– MC simulation, detector R&D etc.

Collaboration:– A quite large collaboration should be necessary to construct

this kind of large scale spectrometer (cost & man power).– Experiments which use similar systems should be gathered.

Dec. 1, 2005 S. Sawada / J-PARC-HS05 26

Summary

Propose to study high-mass dimuon production with a high-rate spectrometer.

A rich physics program in Drell-Yan and J/ production can be pursued using the spectrometer.

Fermilab experiments are our starting point. 50 GeV proton beam with 2x1012 protons per spill is r

equested. 30 GeV proton beam would also be interesting for stu

dying the J/ production. Also propose to construct a high-momentum beam lin

e.