changyi zhou (mcgill university ) on behalf of zeus collaboration

Changyi Zhou (McGill University )

on behalf of

ZEUS CollaborationFebruary 26, 2008

C. Zhou (McGill Univ.)ECT *– Trento, February 25-29,

2008 2

Outline Analysis motivations Previous publication and results Experimental setup and observation

principle Data sample selection and K0

s mass distribution

K0sK0

s spectra with interference fits Non-interference function Interference function

Summary and conclusion

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 3

Motivations The Standard Model explains the existence

of hadrons well. The Standard Model allows for the

existence of particles made by gluons. A gluon carries both a color and an anti-

color. Either two or three gluons may confine

together as color singlet GLUEBALLs

Examples of glueballs



The K0sK0

s system is expected to couple to scalar and tensor glueballs

K0s: has S=0, P=-1, C=+1

K0sK0

s : has P=+1, C=+1 J = even

Motivations (Cont.)

Question: What is the mixing fraction

of mesons and glueballs?

Hybrid? Tetraquarks? Flavor octet states?



Motivations (Cont.)



Previous Publication “K0sK0s Final State in two photon collisions and implications for

glueballs” (L3) Published in Phys.Lett.B501:173-182,2001 (hep-ex/0010037)

~4σ for fJ(1710)

7

HERA


ECT *– Trento, February 25-29, 2008

8

HERA and ZEUS



9

Tracking DetectorCentral Tracking Central Tracking

Detector (CTD)Detector (CTD)

e p

Micro-Vertex Micro-Vertex Detector (MVD)Detector (MVD)

25-35 25-35 m resolution for vertical m resolution for vertical incidenceincidence

official coordinate resolution ~160 official coordinate resolution ~160 mm



Two V0 candidates

K0sK0

s states observation principles

π+

π-

pπ+

pπ-K0s

pk1

π+

π-

pπ+

pπ-pk2

K0s

Decay Length

IP

Pri. Vtx

Sec. Vtx

Collinearity Angle



DATA Sample and Event Selection

The data sample is dominated by 90% photoproduction, while 10% is Deep Inelastic Scattering



K0s mass distribution

Full sample contains:

1300509 K0s

672418 K0sK0

s



Modified Relativistic Breit-Wigner (MRBW) function:

Fitting functions

Background function:

• Ci is the amplitude of the resonance• m*,i is the mass of resonance• Гd,i is the effective resonance width• M is the K0

sK0s invariant mass

• A, B, C are free parameters

• mK0s is the K0s mass from PDG



Fitting using Breit-Wigner with no interference

The dip between f2(1270)/a2(1320) and f2(1525) is due to the constructive interference between the states.

The structure around 1270 region is due to the destructive interference between f2(1270) and a2(1320)

JPC= 2++ 2++ 2++ JPC= 0++



Fitting using Breit-Wigner with interference

No interference fit Interference fit

WA102




2/)( dduu 2/)( dduu ss

2

1)3

1

3

1

3

2

3

2(

2

1)3

1

3

1

3

2

3

2(

3

1

3

1

Function = a {5 * BW_f2(1270) – 3 * BW_a2(1320) + 2 * BW_f2(1525)}2

+ b {BW_f0(1710)}2

+ c Background U(M)

a b c are free parameters

BW is Relativistic Breit-Wigner function:




Improved fitting in 1270 and 1420 region, where destructive and constructive interference are well described.

Х2/ndf = 86/110



Summary



Conclusion

Inclusive ep → K0s K0

sX decay production was studied with

all ZEUS statistics (0.5 fb-1)

Clear evidence for f’2(1525) and f0(1710) resonance state

with large statistical significance

Very competitive measurements on peak position and

width for f’2(1525) and f0(1710) are done with interference

fit and compared well with the PDG values

changyi zhou (mcgill university ) on behalf of zeus collaboration

Documents

zhou mcgill

fitting functionsect

p ppk2k0sdecay lengthippri

glueballs l3

motivations cont

flavor octet states

free parametersbw

photon collisions