M Barbi

Slide1: 

Exclusive Vector Meson Production and Inclusive K0SK0S Final State in DIS at HERA Outline: Exclusive vector meson production Summary First observation of resonances in inclusive KS0KS0 final state in DIS Summary Photon2003, Frascati 07-11/04

Slide2: 

VM (MVM) At HERA: q VM |P VM = r, w, f, J/y , y(2S), etc At low |t|  Gluon from fit to F2 scaling violation  soft hard x≈1/W2 Transv. size of the interaction region Small size. No W dependence.

Slide3: 

Fit s µ Wd : » 0.22 for r0, w, f » 0.8 for J/y A first look:

Slide4: 

J/ Photoprod. in bins of W and comparison to LLA calculations Leading Log. Approx. (LLA) pQCD with different gluon parametrisations Models sensitive to input parametrisation of the gluon density Looking at high MVM (consistent with hard regime  previous slide) Indeed, MVM is a hard scale

Slide5: 

And the power-law W dependence?  Can Q2 provide a hard scale?

Slide6: 

Q2 also provides a hard scale. Can Q2 provide a hard scale? J/y already steep at Q2 = 0 Data fitted with Wd pQCD models consistent with data

Slide7: 

p  Y p  Y p  J/Y Photoproduction of proton-dissoc. VM at high |t| What about |t|?

Slide8: 

Q2 , MVM2 and |t| set a hard scale. Perturbative QCD predictions agree with data Summary

Slide9: 

K2(1430) 0 K2(1430) 0 K2(1430) + f2(8) f2(1) a2(1320) 0 a2(1320) - a2(1320) + K2(1430) - K0(1430) 0 K0(1430) 0 K0(1430) + f0(8) f0(1) a0(????) 0 a0(????) - a0(????) + K0(1430) - Tensor JCP=2++ Nonet Scalar JCP=0++ Nonet f0(1710) is a glueball candidate 3 candidates for 2 spots QCD predicts the existence of hadrons made up by gluons (glueballs). From Lattice QCD calculations, the lightest glueball has JCP=0++ with a mass 1730±100 MeV. KS0KS0 couples to meson states with JCP=(even)++

Slide10: 

Þ A total luminosity of 121 pb-1 was used Þ Only events with at least 2 KS0 were selected Þ Clean KS0 sample

Slide11: 

First observation of JCP=(even)++ in DIS. Two states are observed a state consistent with f2’(1525) X(1726) (is this the f0(1710) ?) A third state is observed in the (problematic) 1300 MeV mass region, consistent with the f2(1270)/a2(1320) interference Several states have been observed in the 2GeV region (see PDG02) M. Barbi

Slide12: 

Pz(KsKs)andlt;0 (7%) Pz(KsKs)andgt;0 (93%) Increasing xp More gluons Þ KS0KS0 in the Breit-frame

Slide13: 

First observation of resonances in KS0KS0 final state in DIS was reported Two states are observed in the 1300 MeV, 1500 MeV mass region consistent with f2(1270)/a2(1320) and f2’(1525) Another state X(1726) is observed, probably the f0(1710) (a glueball candidate) States are produced in a gluon rich environment Summary

Slide14: 

Slide15: 

e' e p p' g* VM (MVM) e' e p Y (MY) g* VM Wgp Elastic Proton Dissociative Q2 = g* virtuality; Q2 andlt; 100 GeV2 Wgp= g*p CMS energy; 20 andlt; Wgp andlt; 290 GeV t = 4-mom. transf. squared; |t| andlt; 20 GeV2 VM = r, w, f, J/y , y', U R = 1/[ z(1-z) Q2 + mq2]1/2 ; z = Eq / Eg* |P |P

Slide16: 

( Donnachie-Landshoff ) s rising weakly with W: At low |t|, |t| andlt; 1.5 GeV2 d = 0.22 s steep exponential t dependence (shrinkage): Photon transversally polarized ; low Q2 or |t| ( Shrinkage )

Slide17: 

Photon mainly longitudinally polarized Large Q2 , MVM or |t| ¯ qq system is small, probes the proton Two-gluon-exchange approach at LO Gluon ladder (LLA approach) Gluon from F2 scaling violations

Slide18: 

Forshaw and Poludniowski fitted the ZEUS data for p-dissociative photoproduction of r0, f and J/y mesons (hep-ph/0107068): Dependence at large |t| not exponential: Þ indication that large |t| may provide a hard scale to apply perturbative QCD J/y

Slide19: 

Þ QCD models FKS and MRT(CTEQ5M) are in good agreement with data

Slide20: 

-andgt; Cross-section suppressed with respect to that of J/y -andgt; Steeper W dependence -andgt; Overall R ≈ 0.166 consistent with pQCD prediction -andgt; Fit WDd  Dd ≈ 0.24 consistent with W dependence for y(2S) y(2S) wavefunction has a node

Slide21: 

J/y already steep at Q2 = 0

Slide22: 

Extras….. KsKs final state

Scalar and Tensor Mesons: 

Scalar and Tensor Mesons q q S=1 L=1 JPC = 0++ JPC = 2++ Masses 1-2 GeV, scalar and tensor mesons much heavier than the pseudoscalars Quark Model (u,d,s) I=0 P = (-1)x(+1)x(-1)L = (-1)L+1 C = (-1)L+S J = 0 or 2 S I Scalars Tensors

Slide24: 

QCD: richer than Quark Model, predicts gluon states with JPC = 0++,2++, I=0 g f0(1370) f0(1500) f0(1710) Observed States mix KsKs final state couples only to JPC=(even)++ and it is CLEAN. This is the golden channel (given statistics) to look for scalar and tensor meson resonances Ks: has S=L=0, P=-1, C=+1 KsKs: has P=+1, C=+1 g J=even Is this a qq state?

Production mechanisms in DIS: 

Production mechanisms in DIS Odderon Exchange VM Radiative decays In quark Jets In gluon jets Gluon rich processes Gluon poor processes

Slide26: 

Fit 3 Breit-Wigner and a backg. function: Problematic region

Slide27: 

cosKK andlt; 0.92 cut Observation of J=even meson resonances in ep

Slide28: 

Þ Attempt to include the 1980 MeV mass region

How well a smooth background describes the data:: 

How well a smooth background describes the data: It is less than 1% likely that a smooth distribution describes the data.

e+e-ggggKsKs: 

e+e-ggggKsKs If f(1710) is a glueball it should have small coupling to gg