Study of in medium mass modification for the φ meson using

φ meson bound state in nucleus

P.B"uhler1, C. Curceanu2, C. Guaraldo2, O.Hartmann1,K.Hicks3, M.Iwasaki4,5, T.Ishiwatari1, P.Kienle6, J.Marton1,R.Muto7, M.Maruki7, M.Niiyama4, H.Noumi8, H.Ohnishi4,S.Okada2, A.Romero Vidal2, A.Sakaguchi9, F. Sakuma4,

S. Sawada7, D. Sirghi2, F. Sirghi2, K. Suzuki1,D.J. Tedeschi10, K.Tsukada4, O. Vazquez Doce2, E. Widmann1,

S. Yokkaichi4 and J. Zmeskal1

29 members from 10 institute

Introduction

Introduction

What is the origin of hadron mass→ Spontaneous breaking of chiral symmetry！Under the extreme condition such as high temperature and/or density, restoration of its broken chiral symmetry has been expected → reduction of chiral condensation value

QGPneutronstar

SPS, RHIC, LHC KEK‐PSJ‐PARC

W.Weise NPA553, 59 (1993).

Mass of the light vector mesons,ρ,ω and φ, will be a good candidatequantity to testing for the direct effect of chiral symmetry restorationin nuclear media

(Progress of Theoretical PhysicsVol. 95 No. 6 (1996) pp. 1009-1028)

Unfortunately, <qq> is notdirect observable itself.

Introduction

QGPneutronstar

SPS, RHIC, LHC KEK‐PSJ‐PARC

W.Weise NPA553, 59 (1993).

T. Hatsuda, H. Shiomi and H. KuwabaraProg. Theor. Phys. 95(1996)1009 Mass of vector meson in medium

will be decreasing when density increasing

From QCD sum rule

What is the origin of hadron mass→ Spontaneous breaking of chiral symmetry！Under the extreme condition such as high temperature and/or density, restoration of its broken chiral symmetry has been expected → reduction of chiral condensation value

φ meson in nuclear media

why are we focusing on φ meson?Mass shift on φ meson in nuclear matter is directly connecting to the in medium change of strange quark condensate <ss>( results from QCD sum rules, )

Direct access to the chiral symmetry restoration in the strangeness sector can be possible via φ meson

φ meson in nuclear media will give us unique information onstrange content of nucleon and nuclear matter

φ mesons in nuclear media- experimental situation

mass shift (~3%) of φ meson have been observed by KEK-PS E325.( with the width getting 3.6 times bigger then the width in vacuum)

- PRL 98(2007)04501photo production of φ meson from Li, C, Al, and Cu at LEPS/SPRING-8

σφN in nuclear media getting much bigger than in free space ( huge width broadening ) - PLB608(2005)215

φ meson production in 158 GeV/cIn-In collisions at CERN/SPS (NA60)

mass shift and width broadeningare not identified (with in detector resolution) - arXiv:0906.1102 [hep-ex]

What is really happening on φ meson in nuclear media

Considering mass reduction in nuclear media

Strong attractive force exist between KbarNThis is confirmed by measurement of 2p->1s x-ray energy in Kaonichydrogen atom

M.Iw

asak

iet a

l.,

PR

L78

(199

7) 3

067

1s

2p

only Coulomb int.-8.6 keV

ΔE = -323 eVΓ = 407 eV

The strong attraction between KbarN lead to the conclusion of mass reduction of Kbar(K-)in nuclear media.

Nucl.Phys.A617(1997)449

Mass reduction = attractive force exist ??? = attractive potential ?

φ-Nucleus interaction？

What we learn from KEK-PS E325 results （PRL98(2007)042501）

3% reduction of the φ meson mass observed ! when we selected slowly moving φ mesons

φ meson in nucleus can be modeled as

φ meson is in the energy pocket created by nuclear potential

Formation of the φ-mesic nucleus??

φ-N bound state?φ-N bound state has already been discussed in year 2000, however totally independent starting point.

Meson-Nucleon bound state with “QCD van der Waals” attractive force (Originally this idea is developed for the discussion of ηc-N bound state)

Binding energy obtained with this analysis is 1.8 MeV/n.

Assume : BEA = BEN x A 2/3 ( like the case of hyper nucleus )binding energy for Copper nucleus (for example) ~ 28 MeV.

Goal of the proposed experiment

3% mass reduction of φ meson has been observed by KEK-PS E325. More detailed study will be performed by J-PARC E16

However, the “origin” of mass shift is not clearly identified yet.

T.Yamazaki and Y.Akaishi claimed in Phys.Lett.B453(2000)1, “invariant mass”

=? “mass reduced in nuclear media”

Goal of the proposed experiment

φ-meson bound state, measurement of binding energy and width, together with the invariant mass study ofφ meson in nuclear media will give us a insight what is the origin of φ meson mass shift

From the bound state, we could deduce what kind of attractive force exist between φ and nucleus (nucleon).

Question is how to measure mass shift which can be compared with theoretical prediction??

P29 together with E16 results may answer the questionOrigin of mass shift and contribution of restoration of chiral symmetry in the mass of vector meson in media (need helps from theory..)

Experimental method

How to identify φ meson bound state

Formation of φ mesic nucleus will be identified with missing mass analysis.

a b

φ

Need to find good elementary process for φ meson production

(π,K) reaction for hyper nucleus formation

How to produce φ with low momentum efficiently?

φ production via p(p,φ)φ reaction

Very interesting production processDouble φ meson production will be dominant around threshold ( 0.9 GeV/c<p<1.4 GeV/c) Only less than 10% physical background

Momentum transfer ~ 200 MeV/c

Once we detect one φ meson in the reaction, partner will also be φ meson Missing mass spectroscopy can bedone with forward going φ meson.

How to produce φ with low momentum efficiently?

Huge Background

However, once one can identify third strangeness in the event, thenevent sample will be almost background free

φ meson production with anti-proton will be primary candidate of the

elementary process for the φ mesoic-nucleus production.

How to ensure φ meson is really in nucleus

Let’s focusing on decay modeMass of the φ meson will be decreasing about 30 MeV.i.e. 1019 MeV – 30 MeV = 989 MeV ~ 2 x MKaonMain decay mode for Φmeson, Φ→K+K-, will be suppress.However, Φ meson is in nucleus. There are many nucleon surrounding them.1019 MeV – 30 MeV + 938 MeV(proton)

＝ 1927 MeV > MKaon+MΛ

i.e. Φp→K+Λ will be a dominant decay mode,if φ meson is in nucleus. (This mode is not suppressed by OZI role ) s

suud

K+

Λ

Φ

p ud

sus

i.e. K+Λ in final state will be a good signal to ensure φ meson in medium

Concept for the experiment

Anti-proton

Nuclear target Reaction

φ mesonbound state

Outgoingφ meson

Missing mass

Spectroscopy

K+

Λ

Decay

Strangeness

tag!!

Detector conceptand

signal expected

Conceptual design of the detectorLarge solid angle charged particle spectrometer (with large gap dipole magnet) Large acceptance for

forward going φ meson(for missing mass analysis)

Large solid angle for the decay particles, K+ and Λ,from φ mesic nucleus

ToF wall

Antiproton

beam

CDC

Target Region

Main spectrometer

Target surrounded by trigger counter

targetbeam

K-K+

background trigger rate estimation Multi-pion production in pbar-p annihilation will be a major background source for the trigger

Assume to construct trigger counter with pion rejection factor 1/100

If we assumed 106 anti-proton beam per pulse,background trigger rate will be less that kHz.

Concerning on beam line

What we need for the proposed experimentp beam with the beam momentum 0.9 -1.1 GeV/cEnough space to install new spectrometer with large dipole magnetLength of the beam line is not the problem.

No decay in flight of beam particle ☺

We would like to perform the proposed experiment at K1.1 beam line

Expected p intensity : 1.0x106 antiproton / pulse (30 GeV, 9uA)

Event rate estimationBasic numbers used for the estimation

Beam intensity Ip = 1.0 x 106 / spill (270 kW operation)Beam momentum used for the experiment = 1.1 GeV/cMomentum transfer = 200 MeV/cp-p →ΦΦ cross section = 2.5μbTarget thickness 2g/cm2 (C, Cu, Polyethylene )

Relative capture rate （sticking probability）Rcapture = exp(-q2/qF

2) , q: momentum transfer, qF: fermi momentum

Event rate estimation (2)

300-500 bound state candidate within 40 days runing time

Assumption in the simulation:Spectrometer missing mass resolution = 18 MeV (σ) Fermi momentum in nucleus is taking into account in

the simulationΓφ in nucleus assumed to be broaden 10 time more

than natural widthbound state with 30 MeV B.E. exist

Blue triangle: Missing mass spectra of unbound φ mesonRed circle : Expected signals

Spectra expected -with different MR beam power condition

50 kW operationw/ 120 shifts data taking

135 kW operationw/ 120 shifts data taking

270 kW operationw/ 120 shifts data taking

Blue triangle: Missing mass spectra of unbound φ mesonRed circle : Expected signals

The Experiment will only be performed with 270kW operation?

62 φ-bound candidate events 165 φ-bound candidate events 330 φ-bound candidate events

Because very small physical background, we will be able to “just” identify bound state with MR small beam power operation

Precise determination, we need high beam power or longer beam time allocation.

Schedule to completeTwo questions

When will we be able to receive “Stage-1 approval” from the J-PARC PAC?When the K1.1 beam line will be ready?

We will ready to taking physics data by end of 2013

Development for the analysis software and simulation also needs as same as hardware construction

Global view Two proposals are submitted to J-PARCto explore the chiral symmetry in nuclear matter

E16Mass shift of vector

mesons (and its width)

Electron pair spectrometer at the J-PARC 50-GeV PS to explore the chiral symmetry in QCD E16

P28 Study of in medium mass modification for the φ meson using φ meson bound state in nucleus

P29φ meson bound state (slow φ meson embedded in nucleus)

“QCD with many body system”

• Detail study of bear φ-N interaction

• structure of state etc.

• Mass reduction(with momentum dependent way)

New guide line by theoryHow to connect <qq>

to the observables(like pionic atom)

Physics must be same Kaonic nucleusHyper nucleus

help

φ meson photo production results

at LEPS, CLAS

Summary

Based on the results reported by KEK-PS E325 (mass shift of φ meson) strongly suggested that the production of φ mesicnucleus can be possible.

The most promising elementary process for the φ mesic nucleus production will be pp→φφ channel.(Background free experiment can be achieved, in principle)

Naïve event rate estimation tells us that 300 events candidate for φ mesic nucleus will be produce per 40 days,with beam intensity, 1x106/spill, for 1.1 GeV/c anti-proton.

Expected beam intensity at K1.1Conditions

Primary beam power : 30 GeV, 9uAAcceptance : 4.1 msr%Production angle : 6 degree No decay in-flight ☺

Pbar production cross sectionParameterization presented by R.P. Duperray et.al ( PRD 68(2003)094017 )

12 GeV/c p-Be; 0 degree 26 GeV/c p-Be; 17.8 degree

12.9 GeV/c p-Pt; 5.6 degree

pbar yield at K1.1

～ 1. M pbar/pulse

Experimental setup

Good tracking chamber and PID detector around targetCylindrical Drift Chamber ＋ Kaon ID detector

φ meson emitted to forward direction must be detect efficiently.

Missing mass resolutionMomentum resolution

Conceptual design of the detector

targetbeam

ToF wall = Resistive Plate Chamber (RPC)• FOPI ToF Wall will be a model• < 65 ps time resolution

• Working well under the magnetic field

Target Region

Aerogel cherenkov counter• n~1.2 will be used

CDC

High density Aerogel made at Chiba Univ.

Aerogel sample n = 1.22 ( ρ=0.95 g/cm3) , 1cm (t)quite good transparency( you can read paper easily

through Areogel.)Stiff. ( easy to handle it )

Two samples are now at RIKEN Test to check # of photon etc. is under the way.

Reflection index (n) of aerigel can be produced with controlled waybetween 1.003 to 1.26

n=1.1 to 1.2 will be used for the proposed experimentFinalizing of the counter design is in progress

FOPI-RPC-ToF

One of the candidatetechnology

FOPI ToF Wall< 65 ps time resolutionWorking well under themagnetic field.

ToF wall

~100 ps Timing resolution need for the ToF wall(designed flight path length is 1.0m)

ToF wall will be installed in the high magnetic field environmentNo detector will be installed after ToF wall

Not care much about material budget

resistive plate chamber (RPC) will be used for the ToF wall

Trigger cherenkov counter

Momentum range for kaons emitted to forward direction200 MeV/c < p < 600 MeV/c

Aerogel n~1.2 will be best choice for the cherenkov radiatorWe are starting to discussion with experts( Kawai-san@Chiba Univ. and Tabata-san @JAXA)about R&D plane and etc.Question; how to read out cherenkov photons?

APD? MPPC?

B.E. = 30 MeV, width 20xΓ0120 shifts data taking

Probability of the event shapecan be explained by onlyun-bound event as a function of beam power