Search for exotics by emulsion

J.Kawada & U.Kose (Nagoya)

Emulsion 3-dimensional Sub-micron tracking detector

π‐K 　 productionRecorded in ballon experiment

～ 100 microns

Possible to detect the short-lived particles.Direct observation of decay topology!!

•X-particle in cosmic ray interaction(1971)•Tau-neutrino at Fermi Lab E872 exp.(2000)

First detection of …

.

.

.

What will we search…?

In CHORUS experiment , a ｂｏｕｔ 150,000 νμ and νμ events have been located in emulsion and fully reconstructed. - 93,807 νμ analyzed event by event and 2,013 νμ induced charm events,-2,704 νμ analyzed 40 charm have been found

CHORUS experiment has a very large number of charm events, it may also produce anticharmed Pentaquarks and charmed hyper nuclei.

CHORUS 　 ExperimentShort Base-Line neutrino oscillation experiment

@ CERN (1994 ～ 1997)

5.06 1019 POTs (1994-1997)

<E> ~ 27 GeV

<L> ~ 0.6 km

Ratio< E > （ G

eV)　 νμ 93.9 ％ 26.9

　 νμ 5.3 ％ 21.7

　 νe 0.007 ％ 47.9

　 νe 0.002 ％ 35.3

　 ντnegligibl

e－

770 kg emulsion target

and scintillating fibre tracker

Calorimeter

Air core spectrometer andemulsion tracker

Air core spectrometer andemulsion tracker Veto plane

Muon spectrometerMuon spectrometer

- -

h-h-

Nucl. Instr. Meth A 401 (1997) 7

CHORUSCHORUS detector detector

CHORUS EmulsionCHORUS Emulsion

71cm

36cm

36plates

Charged particle

350μ ｍ

90μ ｍ

CHORUS Analysis Method

CCD and XYZ stage

CCD and XYZ stage Host CPUHost CPU

Network Network data data

storagestorage

Automatic microscopesAutomatic microscopesUltra Track Selector(UTS)Ultra Track Selector(UTS)

Found track

track shifting

summing

track

Automatic Scanning

CalorimeterAir-core magnet

beamMuon spectrometer

Emulsion target

Interaction vertex

Electronic detector

prediction

Scan-Back Method

All track segments infiducial volume

After a low momentumtracks rejection(P > 100 MeV) and numberof segments 2

After rejection ofpassing-through tracks

Tracks confirmedby electronic detectors

NET SCAN

Decay!

νint

Vtx point

CHORUS 　 Results 1 －　 νμ→ντ 　 Oscillation 　－

No ντ observation

143,742(CC) + 24,184(NC)Events were analyzed

No candidate

　 CHORUS 　 Results －　 charm associating only －

Phys. Lett. B. 613 (2005) 105

Phys. Lett. B. 604 (2004) 11

Phys. Lett. B. 604 (2004) 145

Phys. Lett. B. 575 (2003) 198

Phys. Lett. B. 555 (2003) 156

Phys. Lett. B. 549 (2002) 48

Phys. Lett. B. 539 (2002) 188

Phys. Lett. B. 527 (2002) 173

Phys. Lett. B. 435 (1998) 458

Charmed Hyper Nuclei

D*+ production

D0 production

Antineutrino charm production

Fragmentation properties

QE charm productionΛc productionBR CC associate charm productionD0 production Diffractive Ds

* production

Accepted to Nucl. Phys. BPhys. Lett. B 614 (2005) 155

　　　　　 CHORUS 　 Results 2 －　 Measurement of D0 production －　

Phys. Lett. B. 613 (2005) 105

2 prong (V2) 841 (background: 37) 4 prong (V4) 230 (background:0.25)

Observed D0 events sample: 95450 νμ CC events

6 prong (V6) 3 (background:0.19)(D0)=0.4010.027

(D0)/(CC)=0.0269 ± 0.0018 ± 0.0013

= 0.207 ± 0.016 ± 0.004B(D0 V4)B(D0 V2)

　　　　　 CHORUS 　 Results ３ －　 Anti neutrino charm production －　

Decay topology

Candidate events

Background

2-prongs

16 1.4±0.3

4-prongs

6 0.13±0.06

1-prongs

4 0.8±0.2

3-prongs

4 0.3±0.2

5-prongs

2 0.02±0.01

Total 32 2.7±0.4

(syst)% 1.0(stat) 1.5)(

)( 4.10.1

XN

XcN

Sample: 2,704 νμ CC interactions

What will we do next…?

１． Charmed Pentaquark

２． Charmed Hyper Nuclei

Charmed Pentaquark Search

Θc Production from ν

uud

uudd

d

d

c

ν （ Lepton)+

proton Θ ｃ

W －

Theoretical OverviewΘ0c （ uuddc) 　 Mass prediction

Θ0c　Mass ModelＴｈｅｏｒｉｓ

ｔ

2710 　ＭｅＶ diquark-diquark-antiquark

Ｊａｆｆｅ，Ｗｉｌｃｚｅｋ

2704 　ＭｅＶ skyrme model Ｗｕ , Ma3445 　ＭｅＶ lattice QCD Sasaki

2985 　ＭｅＶ diquark-triquarkＫａｒｌｉｎｅｒ，Ｌｉｐｋｉ

ｎ

Ｉｆ Θc mass is bellow DN threshold (2807MeV)Θc can decay “Weakly”

Weak

Weak

Strong

Strong

→ 　 lifetime of Θc can be expected to be in the range of other charm hadrons.

Experimental Evidence at Experimental Evidence at H1H1

hep-ex/0403017hep-ex/0403017

•Only one evidence by H1 Collaboration: m=3099 MeV can be Only one evidence by H1 Collaboration: m=3099 MeV can be

considered as pD* stateconsidered as pD* state

•ΘΘcc (3099) can be considered as an excited state (chiral partner) (3099) can be considered as an excited state (chiral partner)

of the predicted ground pentaquark state of the predicted ground pentaquark state ΘΘcc(2710)(2710)

M. Nowak et al, hep-ph/0403184M. Nowak et al, hep-ph/0403184

Possible decay Mode of Θ0c

Strong Decay

　 Θ0c 　 →　 Ｄ＊－　Ｐ　　　　　 →　 Ｄ＊ 0 ｎ　　　　　 →　 Ｄ－ Ｐ　　　　 　　 　 →　 Ｄ 0 ｎ　

Ｗｅａｋ Decay

　 Θ0c 　 →　 θ ＋（ Lepton) － ν 　　　　　 →　 θ ＋ π －　　　　　 →　 Ｐ π －Ｋｓ０　　　　 　　 　 →　 Ｐ Ｋ＋ π － π － ( golden topolog

y) 　　　　　　　　　　　　：　　　　　　　　　　　：

Above threshold

Below threshold

Background of Θ ｃ

Main background in emulsion are D0 , K0 and Λ0 decay. And neutron , K0 and Λ0 interaction without any visible nuclear breakup at the interaction point.

How to Detect and Identify ?

Proton Identification to eliminate D0 B.G.

　 D0 → 　 K － π+ (2-prongs) 　　　　　 →　 K0π+π － (2-prongs) 　　　　 　→　 K － π+π+π － (4-

prongs) 　 : :

Any way , no proton in daughters.

cτ=123μm

Proton ID is the key to distinguish Θ0c and D0!!

Proton ID by dE/dX and P.H.

..…..

1.2GeV/cπ

1.2Gev/c P

Test experiment@KEK

T.Toshito et al. N.I.M A516(2004)436-439

dE/dX VS Momentum(GeV/c)

PKπμ

separatable region

How to Detect and Identify ?

Topological analysis to eliminate Λ0 B.G.

Λ0 decay mode

Λ0 　→　Ｐ π －　　 2-prongs （ 63.9 ％）　　　　→　ｎ π0 　 all neutral （ 35.8 ％）

cτ=7.89cm

2-prongs only ( also Ks0 ).

4-prongs decay is only for D0,Θ0c.

summary of Identification

4-prongsdecay mode

proton daughter

Θ0c Yes Yes

D0 Yes No

Λ0 No Yes

Ks0 No No

If 4-prongs decay have proton daughter, it could be Θ0c !!

So far…

Decay topology

Candidate events

Background

2-prongs

16 1.4±0.3

4-prongs

6 0.13±0.06

1-prongs

4 0.8±0.2

3-prongs

4 0.3±0.2

5-prongs

2 0.02±0.01

Total 32 2.7±0.4

We have already found6 , 4-prongs decay ,in 2,704 νμ int.

estimation of lifetime

P[GeV/c] = 1.5 × λ ｰ 1

λ 　＝　＜ θdecay ＞

θdecay

momentum → gamma factor → estimated “cτ”

D0

measured in emulsion

<θdecay>

D0 Momentum[GeV/c]

MC simulation

Estimated cτ for 4-prongs decay

cτ （ D0 ） 123μmEstimated cτ[μm]

About cτ, these 6 eventsare very D0 like.

data MC

How to Detect and Identify ?

Long flight length decay search

So far

6.4mm

10mm

1.5mm 3mm

1.5mm3mm

Θ0c may have long lifetime

This range is never searched before!!

Θ0c search

Near Future plan…

Long Flight Length decay search (Now just started)

Proton ID Research & Development

A little bit far Future plan…?

New experiments to search Pentaquark

Charmed Hyper Nuclei Search

Roughly drawing of charmed hyper-nuclei production

νμP

n P

P PP

PP

n

n

nn

nn

nP

n

Charm hadron interactswith nuclei and Λ+ ｃ is absorbed

μ －

hadron

νμ created μ － andhadrons and charm hadron

Decay

How does it look?

s=1 hyper fragment decayobserved in CHORUS emulsion

Decay pointF.L. is a few microns

M.Miyanishi et al. CERN-PH-EP/2005-017

How to identify a “charmed”

1. Energy release is bigger than “stranged”.

→ Stranged Hyper-Nuclei can’t exceed 200 MeV.

2. Charmed Hyper-Nuclei can have s=1 particle as a daughter.

→ K/π/P separation by dE/dX

So far…Searched in 22,200 νμ interactions.

No candidate

　 Upper limit of production rate by 27GeV νμ

　　　　　　

M.Miyanishi et al. CERN-PH-EP/2005-017

further search will be done…

4109.1)(

)(

XA

XSFA

2103.1)(

)(

XA

XSFA

c

(90%CL)

ε （ＣＣ） /ε （ＨＦ）　＝　０．８７ ± ０．１０

Summary

Emulsion can give the “first direct observation” of pentaquark , and charmed hyper nuclei.

We have already had several thousands of νμ

　 interactions , and analysis is going on.

For charmed hyper nuclei , 22,200 νμ interactions have been analyzed and no candidate have been found. Further search will be done…

Backup

Summary of Identification

proton 4-prongs2-prong

with neutral

Θ0c

D0 no

Λ0 no no

Ks0 no no no

How to Detect and Identify ?

Also 2-prongs…Kinematical analysis to eliminate Λ0 B.G.

2-prongs decay is also possible. If proton ID is done.

no neutral escapeΛ0 , Ks0 case～１００％

θｙ

θｘ

parent

daughter

daughter

neutral escapeD0,Θ0c case

θｙ

θｘ

parent

daughter

daughterneutraldaughter

Flight Length of D0

F.L.(micron)