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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 4

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?

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 5

Motivations (Cont.)

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 6

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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008

8

HERA and ZEUS

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008

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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008

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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 11

DATA Sample and Event Selection

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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 12

K0s mass distribution

Full sample contains:

1300509 K0s

672418 K0sK0

s

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 13

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

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 14

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++

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 15

Fitting using Breit-Wigner with interference

No interference fit Interference fit

WA102

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 16

Fitting using Breit-Wigner with interference

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:

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 17

Fitting using Breit-Wigner with interference

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

Х2/ndf = 86/110

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 18

Summary

C. Zhou (McGill Univ.)

ECT *– Trento, February 25-29, 2008 19

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