pentaquark searches at the relativistic heavy ion collider

Pentaquark Searches at the Relativistic Heavy Ion Collider

Sonia KabanaUniversity of Nantes and SUBATECH, Nantes,

France

EINN 2005Milos, Greece, 20 Sept. 2005

OutlineOutline

• Introduction• Pentaquark Searches in STAR

theta++Xi0/N0theta+Xi--

• Pentaquark Searches in PHENIXanti-theta-

• Conclusions and outlook

IntroductionIntroduction

Relativistic Heavy Ion Collider at Brookhaven Lab:RHIC energy <= sqrt(s)=200 GeV per NN collisionsCollisions studied: AuAu, pp, dAu, CuCuFour experiments: Phenix, Star, Phobos, BrahmsPhysics goals:

-QCD phase transition at Tc 200 MeV new signature seen: jet quenching-Spin of the nucleon

PR

L 92

(20

04

) 05

23

02

; PR

L 91

(20

03

) 18

23

01

What is special about RHIC for exotic particle searches ?What is special about RHIC for exotic particle searches ?

STAR, PHENIX: Elliptic flow of hadrons scales with the nr of quarks -->Data suggest hadron formation through quark coalescence --> quark coalescence as new production mechanism opens up for multi-q/g states

Measurements from Heavy Ion Collisions at SPS and RHIC suggest strongly that a new state of matter is formed in these collisions made by (100eds) of deconfined quarks and gluons

RHIC may be a unique source of multiquark and gluon states made by coalescence possibly out of a hadronizing QGP

STAR

PHENIX

STAR identification capabilities used in this study:

TPC inside a magnet, dE/dx id, topological id for decays in the TPC STAR is able to detect many strange particles in large acceptance (full phi, =-1,1): , , 0s, , , (1530), (1520), K+- etc.

Dedx plot

One event p+p with a Xi or L embedded to illustrate the topological cuts

STARSTAR

STAR theta++/+, Xi-- SearchesSTAR theta++/+, Xi-- SearchesXi-- -> pi- Xi-+ p + KS

++ p + K+

Data Set:Au + Au 200 GeV run 2 (~1.7 M, 30-80%) p + p data 200 GeV run 2 (~6.5 M, Z<75cm)d + Au 200 GeV run 3 (18.6 M)Au + Au 63 GeV run 4 (5.6 M)Cu + Cu 63 GeV run 5 (16.5 M)Au + Au 200 GeV Run 4 (10.7 M, 20-80%)

H. Huang, Y. Ma, S. Salur, C. Markert

Results shown in : J Ma, APS april 2005, H Huang Beijing june 2005, H Huang, DNP Hawai 19-25 Sept 2005

pK+ and pK- from 18.6 M d+Au at 200 GeV

dAu results

M (GeV/c2)

dAu results

The invariant mass distribution is fitted to a Gaussian plus a linear function. A 3.5-5.0 sigma signal is seen Measured mass is about 1.53 GeV/c2. Full width is about 15 MeV

+++p and using as K

K

Slope depends on the levelof pion contamination (p cut) !

Other PID Cuts

Kaon 0.2<p&pt<0.7, Proton 0.3<p&pt<1.0

AuAu 62.4 GeV Results

AuAu 62 GeV data20-80% centrality bin5.6 M eventsWeak Signal (3sigma) if any

Kaon p&pt (0.2, 0.6)Proton p&pt (0.3, 1.5)

Year 4 AuAu 200 GeV data20-80% centrality bin10.7 M eventsNo Significant Signal (2)Kaon p&pt (0.2, 0.6)

Proton p&pt (0.3, 1.5)

AuAu 200 GeV Run 4 Results

Cu+Cu 62.4 GeV Run 5 Data

Year 5 CuCu 62 GeV data0-70% centrality bin16.5 M eventsNo signal at all !!

Kaon p&pt (0.2, 0.6)Proton p&pt (0.3, 1.5)

Is There an Obvious Contradiction ?

The signal is not significant in Au+Au systems

d+Au a favored system ?: signal strength and low combinatorial background --> RHIC should have another long d+Au run

A Stringent Limit from HERA-BA Stringent Limit from HERA-B

HERA-B hep-ex/0408048sqrt(s) 42 GeVpA (C,Ti,W) 200 M inelastic events+/ <0.92%; 95%CL+/(1520) <2.7%; 95% CL

Our Estimate in STARd+Au sqrt(s) 200 GeV/ ~ 0.35%

Does this imply (1520)/ ~ 34%?

STAR(1520)/ ~ 10% (corrected for branching ratio) !

Spectrum?

Spectrum includes ++ and -- Mt-exponential fit yields:dN/dy = 0.0012 +- 0.0006T = 315 +- 30 MeV

Yields for some particles in dAuKs: 0.321 +- 0.006 +- 0.03L+Lbar: 0.339 +- 0.007Xi+Xibar: 0.0251 +- 0.0006Phi: 0.0642

After acceptance and efficiency correction

Assuming 100% branching ratio

++/ ~ 2%

−−→ )1530(

+−→ )1530(

+−++ →

−−−− →

Data: dAu MinBias, 15M events. Black lines are from event mixing. Clear signals were seen for the (1530) particle. No signal for the -- has yet been seen.

From 14,000 -

From 11,600 +

STAR Preliminary

Invariant Mass (GeV/c2)

Invariant Mass (GeV/c2) Invariant Mass (GeV/c2)

Invariant Mass (GeV/c2)

Jingguo Ma, UCLA APS Meeting

05/01/2004

Xi-- STAR searchesXi-- STAR searches

Minv [GeV/c2] Minv [GeV/c2]

Star Preliminary d+Au

Star Preliminary p+p

Cou

nts

?

Star Preliminary p+p

Signal

Mixed Event

Background

?

2 MeV bin size

Sevil Salur, Yale Univ. APS Meeting 05/01/2004STAR theta+ --> pK0s searchesSTAR theta+ --> pK0s searches

dAu data, Ks0 was identified by topological method

There is some excess at invariant mass around 1540 MeV/c2, but it is not too significant statistically.

STAR Preliminary

0)( spKsuudd →+

J Ma, APS april 2005

STAR Xi0/N0 --> L K0s searchSTAR Xi0/N0 --> L K0s searchS. Kabana, R. Witt, M. Heinz

S. Kabana, 20th Winter Workshop on Nuclear Dynamics

Jamaica, 15-20 March 2004

Identification of and K0s in the present study

Topological cuts:

- Search for p - and K0s + - decay pattern (V0, requiring sec. decay vertex)

- Distance of Closest Approach (DCA) between daughters < 0.8 cm

- DCA of V0 to primary vertex < 0.4 cm, V0 Decay Length > 6 cm

- DCA of V0 daughters to primary vertex > 1.3 cm (K0s), 1.0 cm p(), 2.5 cm ()

- Accept only unambiguous K0s and , namely satisfying only one hypothesis

- Quality cuts: Nr. of hits(track) > 15 (out of max 45), Avoid same tracks used in both V0s

STAR Au+Au coll. 200 GeV preliminary

De/dx cuts:

- De/dx(tracks) < 3 from expected De/dx

- Momentum(proton) < 0.7 GeV, Momentum(pion) < 0.5 GeV

…..Identification of and K0s in the present study

Data sample:

Au + Au collisions at s(NN)=200 GeV Trigger: minimum bias, 1.45 Million events

-Require a defined primary vertex, with |Z| <25 cm

-Mass range used around the mean to select K0s and : K0s: +-35 MeV, : +-10 MeV


Preliminary results of STAR pentaquark searches in the K0s channel

Observation of a possible narrow peak at 1734 MeV in K0s inv.mass

Au+Au min. bias (s)NN=200 GeV Cut out upper ~10% of (tot) to suppress background

Region +- 3 MeV (~1.5 ) around maximum: S/(B)=30.6/ ( 35.4)= 5.15, S/(S+B)=3.77, Mass = 1733.6 +-0.5 MeV +-5 MeV (syst), < 4.6 +-2.4 MeV (Gauss,1 MeV bin)

Bin size 3 MeV

Blue line: mixed event

background


Best Significance obtained in semiperipheral ev.: S/(B)=19.36/ (10.64)=5.93

No cut on centrality


S/(B)=40.55/ (83.45)= 4.44

(1232) p() pi-(K0s) + K0s(pi+ pi-) = 1232+497.67 = 1729.7 MeV

Could fake possibly a peak near 1734 MeV ? Note STAR syst. error ~ 5 MeV

- Difficult to result to a narrow peak ( width ~120 MeV)

--Test 1: Cut more on DCA(p,pi) to primary vertex does not destroy the peak

Test 2: Cut Inv.Mass( p() pi-(K0s) ) out of mass +- 30 MeV does not destroy the peak


Phenix is the only experiment which could search up to now for the

anti-theta- --> anti-n K-

Decay channel, thanks to its ability to identify antineutrons in the electromagnetic calorimeter

Antiparticle/particle ratios at RHIC are high: >=0.7

PHENIX pentaquark searchesPHENIX pentaquark searches

K-

`n

Simulated- K- +n

Dch+PC1

PC2

EMC+PC3

Anti Pentaquarks in PHENIXAnti Pentaquarks in PHENIX

Looks fairly straightforward: Search for a big cluster in the electromagnetic calorimeter caused by ann annihilationand combine it with a K

-

0+p Fairly hopeless due to small acceptance(three particles in small aperture)

But how about the Anti Particle?

- K- +n

+ K++nNeutron difficult to identify in PHENIX

K identification up to p=1.5 GeV using TOF (EMCAL), momentum from central tracker

EMCal response for p and anti-p. The annihilation energy of anti-p leads to larger clusters, which is a signature also for anti-n identification.

C. Pinkenburg, QM2004

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.



PHENIX anti-theta- --> K- anti-n identification capabilities PHENIX anti-theta- --> K- anti-n identification capabilities

Reliability of Anti-n CandidateReliability of Anti-n Candidate

pT [GeV/c]

mas

s pe

ak [G

eV/c

]

Marker : Data

Dash line : MC

-

+

mas

s fr

om P

DG

– Invariant mass peak of

-(1189.4) n + - : R.R. 99.85%, c-= 2.396cm

+(1197.4) n + + : B.R. 48.31%, c+= 4.434cm

• Mass shift due to no TOF calibration for n in EMCal is <~5%

• Quick check by Monte-Carlo shows agreement with data

- +

1.1 1.2 1.3 1.4 1.5 1.6 1.1 1.2 1.3 1.4 1.5 1.6

Cou

nts

/ bin

n + - n + +

No pT cut No pT cut

200 GeV p+p 200 GeV p+p

Same event

Mixed eventMinBias trigger

Invariant mass [GeV/c2]

No signal seen in the channel K+ anti-n, in which no signal is expected.

K+ anti-n inv. mass






K- anti-n inv. mass

While a signal was visible near 1.53 GeV without a needed timing correction for the anti-n in EMCAL, after this correction was done the signal dissapeared.

--> Anti-sigma- signal is 2 times larger without timing correction


No signal seen for anti-theta- --> K- anti-n with timing correction Remaining Mystery: why no signal in K+ anti-n without timing correction?

C Pinkenburg RHIC AGS meeting may 2004

Data SetsData Sets

• dAu @ s=200GeV ~500*106 Events

• pp @ s=200GeV ~50*106 Events

• AuAu @ s=200GeV ~36*106 Events

• From rough simulations we estimate a 0.2% reconstruction efficiency for the-

• dAu @ s=200GeV ~500*106 Events

• pp @ s=200GeV ~50*106 Events

• AuAu @ s=200GeV ~36*106 Events

• From rough simulations we estimate a 0.2% reconstruction efficiency for the-

- K- +n (pp) - K- +n (pp)

Statistically challenged analysis,So far no signal (we hope for the manypp events we are going to take in Run5)

Courtesy of Hisayuki Tori

- K- +n (AuAu)- K- +n (AuAu)Top 30% central 30-50% 50-92%

work-in-progress

work-in-progress

work-in-progress

Small plots but trust me there is currently no signal either

Courtesy of Masashi Kaneta

We now have 50 times more AuAu events from Run4!

Masashi’s thermal model predicts -/+~0.1 for central events (assuming J=1/2 for the -). Testing this should be within reach.

Future plansFuture plans• We probably can reduce the background in our K- n

invariant mass distribution• Improve the EMCal Hadron timing, that will hopefully

bring the masses closer to pdg• We can recover nearly a factor of 2 of Anti Neutrons

by recovering broken up clusters• The look very promising, we can do upper limits on

ratios since the and K efficiencies are known and the difficult Anti Neutron efficiency drops out

• 1.5*109 fresh AuAu Events @ s=200 are waiting for us

• We probably can reduce the background in our K- n invariant mass distribution

• Improve the EMCal Hadron timing, that will hopefully bring the masses closer to pdg

• We can recover nearly a factor of 2 of Anti Neutrons by recovering broken up clusters

• The look very promising, we can do upper limits on ratios since the and K efficiencies are known and the difficult Anti Neutron efficiency drops out

• 1.5*109 fresh AuAu Events @ s=200 are waiting for us

Comment: Present limit of momentum of K- to enable TOF id and related pi contamination, allows for AntiSigma- detection, but is this good enough for a much rarer pentaquark signals ?

--> Small searched signal implies need to reduce the background more than needed for detection usual hadrons (Lambdas, Sigmas..)

--> Would be clearly of interest to select K- in the momentum region with the smallest possible contamination and look for pentaquarks with this sample !



Heavy Ion collisions at RHIC may offer a unique opportunity to produce multi-q/g states through coalescence out of a QGP

- PHENIX: searches for anti-theta- --> K- anti-n

--> no signal found in dAu, pp anf AuAu collisions at sqrt(s)=200 GeV

--> studies with lower pi contamination important, higher stat AuAu to be analysed

-STAR: - Peak seen in theta++ and theta-- channel in d+Au collisions at sqrt(s)=200 GeV consistent with detector resolution, and below UL of HERA for theta+

- Low significance in Au+Au at 62 and 200 geV

- No peak seen in Cu+Cu 62 GeV

Conclusions and outlookConclusions and outlook

Conclusions contConclusions cont

theta+ --> p K0s : No significant peak seen in pp, dAu and AuAu collisions --> Ongoing work

N0/X0 --> LK0s : peak seen at m=1734 MeV, width consistent with the det. Resolution and S/sqrt(B)=5-6 in Au+Au collisions at 200 GeV

Future plans for both Phenix and STAR include analysis of more data : 2004 AuAu 200 GeV 2005 Cu+Cu 62 and 200 GeV, pp at 200 GeV

To search and confirm or reject the seen candidates: Theta++(1530) and N0/Xi0(1734) and search for anti-theta- , theta+ and Xi--

--------- THE END--------- THE END

STARSTAR

Central Event

(real-time Level 3)

Au+Au Collisions at RHICAu+Au Collisions at RHIC

Possible Sources of BackgroundPossible Sources of Background

Double Conversion of 0 photons

0 e+e- e+e-

Same-sign e’s within the K and p bands

mostly in the low mass region opening angle cut very effective

Associated production K+ p

These background sources contribute to the residuals in the event-mixing. But they do not produce a narrow peak !

in p+p, d+Au and Au+Au collisions at 200 GeV

Sevil Salur

Yale University

Talk given in the APS meeting, Denver, 05/01/2004

and

Poster presented in this meeting

STAR theta_ --> K0s p searchesSTAR theta_ --> K0s p searches

Reconstruction OUTPUT

STAR Preliminary

Signal

Mixed Event Background

Signal after Background Subtraction

One MC (Tinv slope =250 MeV ) is embedded in each real p+p event.

Only 3% of these ’s were reconstructed after cuts.

The width and the mass remain consistent with the MC input after the reconstruction.

Monte Carlo INPUT

Simulation Studies II

(10 MeV ) (1.54 GeV/c2 )

Sevil Salur, Yale Univ. APS Meeting

05/01/2004

Proton K0s

Momentum Distributions from Monte Carlo +

Identified from real events.

Simulation Studies

Cuts to optimize signal over background

can be reconstructed in

this PT and y range

PT [GeV/c]

NE

ntri

es

NE

ntri

es

PT [GeV/c]

Sevil Salur, Yale Univ. APS Meeting

05/01/2004

Feasibility Studies with current Au+Au dataFeasibility Studies with current Au+Au dataW. Liu, C.M. Ko Phys.Rev.C68:045203,2003 J.Letessier, G.Torrieri, S.Steinke and J.Rafelski hep-ph/0310188 Jorgen Randrup nucl-th/0307042

~0.5-1.5 per event for AuAu

Sevil Salur, Yale Univ. APS Meeting 05/01/2004

•0.5-1.5 X 1.5 Million 0.8-2.3 Million

•Efficiency 3% 25-70 K

•Branching Ratio 50% 10-35 K

•BR 50% from K0 s 5-17K

Background pairs per event in the mass range of is 2.

•2 X 1.5 Million 3 Million

Significance = Signal/√(2 X Background+Signal)

2-7

−+ + KppK +−+ KppK

++ and (1520) Using the Same Analysis Procedure

(1520)

Same charge Sign (SS) and Opposite Sign (OS) background different

Background Shape Depends on Cuts

M (GeV/c2)M (GeV/c2)

K [0.2-0.6] GeV/cP [0.3-1.5] GeV/c

K [0.2-0.6] GeV/cP [0.3-1.0] GeV/c

Monte Carlo 1733 K0s

Momentum of K0s is lower than of

Suggests cut : mom(K0s) < ~1 GeV

1733 K0s generated (inv. Slope(mt)= 500 MeV)

1730 K0s in detector acceptance.

Generated with: y=-1.5 to 1.5, inv. Slope(mt) = 250 MeV, width=1 MeV

K0s

STAR preliminary

+pK −Kp

−+ + KppK

Can the Peak Be Real ??

Other PID Cuts

Kaon 0.2<p&pt<1.0, Proton 0.3<p&pt<1.5, no opening angle cut

STAR N0/X0 searchesSTAR N0/X0 searches

Bin size= 1.5 MeV, Fit: Breit Wigner + polyn. Mom(proton)< 0.9 GeV mom(pi) < 0.7 GeV

Detector resolution (1730 K0s ) ~ width = 6.3 ± 1.7 MeV --> measured width of 4.6 +-2.4 MeV is consistent with the exp. resolution within errors

Mass= 1729 ± 0.7 MeV

Monte Carlo 1730 K0s

Mass=1730 MeV, Breit Wigner Width=1 MeV, inv. Slope(mt)=250 MeV, y=(-1.5,1.5)

Geant + embedding in real data from p+p collisions at 200 GeV

Investigations of systematic errors:

-Split track investigation: Cut on nr of hits(tracks) > 25 (maximal possible 45)


Split track investigation II :

| MomentumZ(pos. track(Lambda) – MomentumZ(pos. track(K0s) | > 30 MeV

| MomentumZ(neg. track(Lambda) – MomentumZ(neg. track(K0s) | > 30 MeV


| MomentumZ(pos. track(Lambda) – MomentumZ(pos. track(K0s) | < 30 MeV

| MomentumZ(neg. track(Lambda) – MomentumZ(neg. track(K0s) | < 30 MeV


| MomentumZ(pos. track(Lambda) – MomentumZ(pos. track(K0s) | < 100 MeV

| MomentumZ(neg. track(Lambda) – MomentumZ(neg. track(K0s) | < 100 MeV

Same result when this cut is performed additionally in pT

Testing self-correlations arising from same tracks used in both V0’s:

-- Plot inv. Mass if positive tracks have the same id -> no entries

-- Plot inv. Mass if negative tracks have the same id : 8 entries all around 1.663 GeV

Cos(theta*) of in the ( K0s) parent rest frame

Inv. Mass( K0s) = 1733 +- 3 MeV Inv. Mass ( K0s) < 2 GeV


pT( K0s) parent

(uncorrected)

What could the Lambda K0s peak at 1734 MeV be ?

- PDG states nearby : N(1710) N(1730) has large width ~100 MeV

- Partial wave analysis suggests two new narrow N states at :

1680 and/or 1730 MeV width < 30 MeV (nucl-th/0312126, R Arndt et al)

-Cannot be the 0 I=3/2 pentaquark because K0s decay violates isospin

-It is a candidate for two pentaquark states:

^0 I=1/2 K0 (1st octet, expected m~1700 or ~1860 MeV)

N^0 anti-K0 (2d octet, expected m~1730MeV, or anti-10)

The K0s channel allows to separate the I=1/2 (octet) from I=3/2 (anti-10)

No peak near 1860 MeV disfavours picture of degenerate 8 and anti-10

Is there a way to resolve the ambiguity (ussdd*) or N(uddss*) ?

Yes

Through the measurement of their isospin partners:

N+ K+ and - I=1/2 K-

Correlated diquark model (B Jaffe, F Wilzcek): octet and anti-10 are degenerate

(Diakonov et al) : two octets (1/2+) below 2 GeV mass, PDG or new:N0(1440) N+(1440)

+(1660)-(1660)

0(1690)-(1690)

Seen

(1535)

Seen(1860)

N+(1710)N0(1710)

-(1950?)

-(1880) +(1880)

0(1950?)

0(1660)

0(1600)

0(1880)

01810)

N(1650-90)

(1750-1800)

Theoretical models: Soliton model, Correl. Quark model, Uncor. Quark model etc

STAR candidate

Inv. Mass of anti- K0s in min. bias Au+Au collisions at 200 GeV

-No peak is observed at 1734 MeV above the background -> ongoing analysis

- This non observation could be understood as a low anti-pent./pent. ratio arising from dominant (a)pentaquark production through quark coalescence:

Anti-N0/N0 ~ (u*d*s*d*s/udsds*) ~ (q*/q)^3 ~ p*/p ~ 0.73 (p*/p value taken from STAR coll., PLB 567 (2003) 167)

Anti-Xi0/Xi0 ~ (u*d*s*s*d/udssd*) ~ (q*/q) (s*/s)^2 ~ (q*/q) ~ 0.90

Favours the N0 hypothesis

STAR preliminary

The detectorThe detector

• Maximal Set of Observables– Photons, Electrons, Muons, ID-hadrons

• Highly Selective Triggering– High Rate Capability.– Rare Processes.

Charged Hadron PID AnalysisCharged Hadron PID Analysis Detectors for hadron PID

DCH+PC1+TOF+BBC = /8, -0.35 < < 0.35

Momentum Resolution

TOF resolution TOF ~ 130 ps.

Hadron PID in m2 vs. p space with asymmetric PID cuts.

• 0.2< < 3.0 GeV/c , • 0.4< K < 2.0 GeV/c, • 0.6< p < 3.7 GeV/c.

€

δp / p ≈ 0.7%⊕1.0% × p (GeV/c)

]1)[( 222 −×

=Lct

pm

- Suppression of charged particle hit background, by vetoing charged particles with a layer of pad chambers (PC3) positioned infront of the EMCal.

- Use of p and anti-p momentum and TOF info to determine features of annihilation signal of anti-p in EMC

- Clusters produced by photons were removed by a timing cut (> 3 nsec) and requiring a poor fit to the shower shape expected for a photon

- Important validation of anti-n identification and method for anti-theta- searches :

* through measurement of the

anti-Sigma- --> pi+ anti-n

* through study of the channel K+ anti-n which should not show a signal

Reliability of Anti-n CandidateReliability of Anti-n Candidate• Anti-n momentum resolution

checked– Applying the reconstruction method

to anti-proton

• Comparison of momentum from TOF and tracking

– Resolution<4%,10%,15% in pT<1.0,

1.5, 2.0 GeV/c, respectively

– Momentum shift <~5%

• Anti-n momentum resolution checked

– Applying the reconstruction method to anti-proton

• Comparison of momentum from TOF and tracking

– Resolution<4%,10%,15% in pT<1.0,

1.5, 2.0 GeV/c, respectively

– Momentum shift <~5%

pT [GeV/c]

mas

s pe

ak [G

eV/c

]

Marker : Data

Dash line : MC

-

+

mas

s fr

om P

DG

– Invariant mass peak of

-(1189.4) n + - : R.R. 99.85%, c-= 2.396cm

+(1197.4) n + + : B.R. 48.31%, c+= 4.434cm

• Mass shift due to no TOF calibration for n in EMCal is <~5%• Quick check by Monte-Carlo shows agreement with data

- +

1.1 1.2 1.3 1.4 1.5 1.6 1.1 1.2 1.3 1.4 1.5 1.6

Cou

nts

/ bin

n + - n + +

No pT cut No pT cut

200 GeV p+p 200 GeV p+p

Same eventhigh pT photon trigger

Mixed eventMinBias trigger


work in progress

•Run3 ÖsNN = 200 GeV d+Au• Minimum bias trigger• 91 M events• 5 MeV/c2 per bin

Same event

Mixed event

Cou

nts

/ bin

K + +n in p +p, d+Au, Au+AuK + +n in p +p, d+Au, Au+Au

Top 30% central 30-50% 50-92%

work in progress

work in progress

work in progress

Same event

Mixed event

•Run2 sNN = 200GeV Au+Au– Minimum bias trigger

– 36M events– 4 MeV/c2 per bin

Cou

nts

/ bin

No significant signal seen

•Run3 Ös = 200 GeV p+p• Minimum bias trigger• 35 M events• 5 MeV/c2 per bin

work-in progressSame event

Mixed event

Cou

nts

/ bin

More Strangeness at PHENIXMore Strangeness at PHENIX• From combinations of ±, K±,

p,p, andn• From combinations of ±, K±,

p,p, andn


0

K0s pT =1-2 GeV/c


pT =1-2 GeV/c


K*0

pT =1-2 GeV/c


Not enoughstatistics..

pT =1-2 GeV/c


pT =1-2 GeV/c


pT =1-2 GeV/c


pT =1-2 GeV/c

• Demonstration from– Run3 sNN =200 GeV p+p

– ~24M events of Min Bias trigger

• Blue histograms– Pair from save event

• Red histograms– Combinatorial back ground

from event mixing from Min. Bias trigger

– Normalization range» solid filled area

Anti-Sigma- --> pi+ anti-n is measured, giving a mass close to nominal mass of 1.197 GeV

Pi+ anti-n inv. mass

Pi+ anti-n inv. mass

After mixed event background subtraction




Summary and conclusions

- +(s), - -(1860), 0(1860), -(1850), (c) candidates observed

- STAR preliminary results show a possible narrow peak in the K0s inv.mass at m=1734 +- 0.5+-5(syst) MeV, width < 4.6 +-2.4 MeV, S/sqrt(B)= 30.6/ ( 35.4)= 5.15, S/(S+B)=3.77. Best S/sqrt(B)=5.93 obtained in semiperipheral events. If this peak reflects a real state, it is a candidate for the pentaquark states:

0 I=1/2 (1st octet) and N0 (2d octet or anti-10) K0s

- This peak is not observed in the anti- K0s channel (work in progress)

-The mass agrees well with the PWA result suggesting two new narrow states at 1680, 1730 MeV (Arndt et al)

- We observe a peak at m=1693+-0.5 MeV with S/sqrt(B)=2.92, candidate for PDG Xi(1690) state. STAR can improve the previous limit of <30 MeV (2002 PDG). Xi(1690) maybe a candidate for the Xi0 I=1/2 pentaquark (1st octet)

- We don’t observe a peak in K0s near 1850,1860 from an octet

Suggests that NA49 observed three anti-10 ’s, disfavouring a degenerate 8 and anti-10 (Jaffe et al), however Br. Ratios may differ in and K0s

Outlook:

- Pentaquark searches in other decay modes e.g. + p K0s (S Salur QM04) are on the way and K+- to find the isospin partners

- New data taken in 2004 will enhance significantly the STAR statistics

STAR – Exciting Physics Program A full TOF and Heavy Flavor Tracker upgrade will greatly enhance STAR’s capability !!

RHIC – Exotic Particle Factory

Heavy Flavor TrackerUsing Active Pixel Sensor

two layers of thin silicon detector 1.5 cm and 4 cm radius Charmed Exotics?!Full Barrel TOF Using MRPC

The machine The machine • Relativistic Heavy Ion Collider• Brookhaven National Lab• 2 counter-circulating rings• 3.834 km circumference• Superconducting magnets(3.5T)• 192 dipoles per ring• 246 quadrupoles per ring• Time between collisions: 0.213 microseconds• Crossing angle: 0• Bunch length: 20 cm• Bunches per ring: 56• Luminosity lifetime: 3-10 hours• Particles per bunch (units 1010):

– Au+Au: 0.1– p+p : 10

• Top energies (each beam):– 100 GeV/nucleon Au+Au.– 100 GeV/nucleon d+Au– 100 GeV polarized p+p

pentaquark searches at the relativistic heavy ion collider

Documents

p p data

mevd p p

q p ksq p

dedx plotone event p

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proton ppt

gev resultsauau

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