ICHEP2006 results from ZEUS (+ one H1+ZEUS combined)

1. ICHEP2006 results from ZEUS(+ one H1+ZEUS combined) DESY seminar“Sneak Preview of ICHEP06 Contribution” 24 July 2006 Yuji Yamazaki (KEK) On behalf of the ZEUS and also H1 collaborations ICHEP2006 results from ZEUS / Y. Yamazaki

2. High-Q2 / BSM search Charged current with polarised e- beam Neutral current with polarised e- beam Combined EW+QCD fit on above two Contact interaction Search for stop production Search for Gaugino/Gravitino Multi-lepton production (e and t) Search for high-pT leptons Heavy flavours Charm cross sectionby D mesons and fragmentation fraction in DIS D* cross sections from HERA-II data Beauty from dimuon (NLO comparison) Beauty in DIS (NLO comparison) D lifetime measurement with the MVD Helicity measurement in inelastic J/y QCD through hadronic final state Bose-Einstein correlation for K0 and K Heavy stable particle production Forward jet production Multijet production at low-x in DIS 3- and 4-jets in photoproduction Prompt g + jet in photoproduction LRG between jets in photoproduction K0 and L production in gp and DIS Inclusive and dijet cross sections in DIS Jet radius dependence of the inclusive jets in DIS Jet cross sections in charged current, HERA-II Diffraction Energy and pT distribution of the leading neutrons in DIS and photoproduction Diffractive D* in gp(NLO comparison) ICHEP preliminary from ZEUS List of subjects made preliminary after EPS2005Red ones are new for ICHEP – covered in this talk ICHEP2006 results from ZEUS / Y. Yamazaki

3. NC cross sections(shown in DIS2006) • Very good agreement • No hint of new physics (unfortunatelly …) • You saw combined H1+ZEUS cross sections earlier today • EW parameters extracted in DIS06 • Now contact interaction limit ICHEP2006 results from ZEUS / Y. Yamazaki

4. Contact interactions (CI) • Generic parameterisation for new physics at much higher energy L than s • Effective Lagrangian for vector CI: • NC with polarisation: sensitive to LL or RR ICHEP2006 results from ZEUS / Y. Yamazaki

5. CI with the HERA-II NC data • Much better limits on: • LL and RR ICHEP2006 results from ZEUS / Y. Yamazaki

6. CI limits interpreted by models • Cut-off scale Ms on large extra dimension~ Order of the Planck scale in the extra dimension world • Leptoquarks (not shown) • Quark radiusHERA-I limit:(+0.85, -1.06)10-16 cmNow:(+0.67, -0.81)10-16 cm ICHEP2006 results from ZEUS / Y. Yamazaki

7. CC cross sections (shown in DIS2006) • Good agreement withNLO QCD theories • How about jets?Naïvely as good as NC • The EW and QCD vertex factorises • High statistics e LH sample ICHEP2006 results from ZEUS / Y. Yamazaki

8. CC Inclusive Jet cross sections (HERA-II) • Jet Et softer, cross section smaller • Inclusive CC cross section OKMultijet more than in the MC ? ICHEP2006 results from ZEUS / Y. Yamazaki

9. Dijets in NC Breit frame, ET > 12 / 8 GeV •  : reconstructed parton momentum • Full HERA-I statistics • The renormalisation scale uncertaintyis small at large  Sensitivity to gluons  Different linesindicate choice ofrenormalisation scale ICHEP2006 results from ZEUS / Y. Yamazaki

10. Jet-radius dependence of the NC jet cross sections • The jet studies at HERA (e.g. the previous slide)uses R = 1 in the longitudinal invariant kT-algorithm • Better to use smaller cone radius for reconstructing decay jets from heavy states (t, Z0, W, Higgs, SUSY ….) • Even R = 0.3 is common • Does the NLO theory correct for smaller radius?Important input to the LHC physics ICHEP2006 results from ZEUS / Y. Yamazaki

11. Radius dependence • R dependence well described by NLOhadr, if not perfect • Hadronisation correction is large at small R ICHEP2006 results from ZEUS / Y. Yamazaki

12. Prompt photon + jet in photoproduction • Similar to dijet process • Constrain PDFs (p, g) • Smaller hadronisation correction • Statistics smallMeasurement at low ET Good agreement with various theorieswith ETg > 7 GeV and ETjet > 6 GeV cut ICHEP2006 results from ZEUS / Y. Yamazaki

13. If the photon has lower energy than the jet … • ETg > 5 GeV, ETjet > 6 GeVEnhancing higher-order diagrams near threshold • kT-factorisation calculation seems better, but why? • To be understood on the theory side ICHEP2006 results from ZEUS / Y. Yamazaki

14. Multijet production at low-x in DIS • Aim: studying angular/kT disordering in multijets • e.g. classic question on DGLAP vs BFKL • Trial 1: azymuthal angle between two leading jets Df • Idea came from H1 • Never less than 120°in the dijet plane for 3-jet events • HCM frame: < 120°if: • Dijet plane “tilted” • Higher ET jet outside the rapidity range Sensitive to high-ET forward jet O(as3) calculation[NLO to 3-jet] reproduces the data g p ICHEP2006 results from ZEUS / Y. Yamazaki

15. DET between leading two jets • Trial 2 • Large imbalance, if there is a jet with ET higher than the 2nd jet outside h range • Angular disordering or FSR by NLO not perfect ? p g Large excess at large DET over the NLONB: LO+PS MC (LEPTO) reproduces the data well angular disordered angular ordered ICHEP2006 results from ZEUS / Y. Yamazaki

16. QCD studies through HFL production • Charm / beauty through the BGF diagram: • Test QCD and production mechanism undermulti-scale: mQ and Q2 and/or ET • If this is understood: • sensitivity to the gluons in the proton ICHEP2006 results from ZEUS / Y. Yamazaki

17. Charm through D* with HERA-II sample ZEUS • NLO (still) describes the data ICHEP2006 results from ZEUS / Y. Yamazaki

18. F2cc(x, Q2) from non-D* charm mesons(HERA-I data) • The stat+syst error from D0 is comparable to D*Approaching close to the uncertainty from the PDF with ZEUS-S fit(to inclusiveDIS data only) ICHEP2006 results from ZEUS / Y. Yamazaki

19. Beauty in gp: pT dependence • b-quark level pTdependence • Uncertainty in the extrapolation is not fully estimated for some of the points. • New points fromZEUS at low-pT • D*m and mm tag • High-pT is OKLow-pT shows slight excesssomething to do with the threshold behaviour? • Analysis from the HERA-II big luminosity awaited This plot is in case the combinedplot above is not approved by H1 ICHEP2006 results from ZEUS / Y. Yamazaki

20. Beauty in DIS (HERA-II) with NLO • Update from previous HERA-I analysis: • Jet in the lab frame • Muons with wider kinematic range (e.g. pTm) • Excess everywhere over NLO ICHEP2006 results from ZEUS / Y. Yamazaki

21. D lifetime using the microvertex detector • Steady progress in understanding the MVD • Alignment, tracking algorithm … ICHEP2006 results from ZEUS / Y. Yamazaki

22. Helicity in inelastic J/y in photoproduction • Colour singlet (CS) only or need colour octet (CO+CS): debate between Tevatron and HERA • Tevatron cross section: need CO • HERA: consistent with CS only • HERA cross section is systematics limitedhelicity of J/y may tell something more • Gluon radiation flips the helicity of J/y ICHEP2006 results from ZEUS / Y. Yamazaki

23. Inelastic J/y: helicity parameters • l: transverse +1, longitudinal: -1 • no big difference between CS and CO big sample! • n: non-zero value shows helicity (double-)flip • Data prefers CS+CO? ICHEP2006 results from ZEUS / Y. Yamazaki

24. Diffractive D* in PHP: NLO comparison • Large cross section difference between HERA and Tevatron (~1/3-1/10) • “factorisation breaking” • Attributed to soft rescattering (a.k.a. gap survival probability) • HERA resolved-gp jet cross section is expected to be suppressed • Measurement: both direct and resolved are somewhat suppressed • How is gp D* ? NLO reproduces the data No sign of factorisation breaking at HERA? ICHEP2006 results from ZEUS / Y. Yamazaki

25. Gravitino search • In the GMSB (gauge-mediated Supersymmetry breaking models): • 10 decays to G and g • G is the LSP Photon + Missing pT • Search onplane Higgs sector mixingparameter ~ ~ ~ F: intrinsic SUSY breaking scaleN: number of the messenger fields L: overall sparticle mass scale M: mass of the messenger particle ICHEP2006 results from ZEUS / Y. Yamazaki

26. Multi-lepton production • SM : Bethe-Heitler processesep el+lp, el+lX • H1 sees excess at high mass • Today: ZEUS HERA-II analysis(up to 2005) on ee/eee and tt(e) ICHEP2006 results from ZEUS / Y. Yamazaki

27. Multi-lepton (1) ee and eee • No excess seen in ZEUS at M > 100 GeV • e+: 1 / 0.8 (ee), 0 / 0.4 (eee) • e: 0 / 0.7 (ee), 0 / 0.4 (eee) ICHEP2006 results from ZEUS / Y. Yamazaki

28. Multi-lepton (2) di-tau • Searched through em pair • Branching ratio 6.19% • 3 evts / 2.0  0.8 expected • Background fromep  emmp : < 0.3 events ICHEP2006 results from ZEUS / Y. Yamazaki

29. High-pT leptons: update on muon channel new • Muon study with the cuts similar to H1 • 04/05 e shown in PRC May • Now 98-05 e/e+ completeNB: H1 ~100pb1 more with 94-97 and 06 data • No excess in ZEUS, both in e and e+ ICHEP2006 results from ZEUS / Y. Yamazaki

30. Muon channel from ep: pTX distribution e+p ep • Distribution after final selection, high purity W • More spectacular events for e, if any ICHEP2006 results from ZEUS / Y. Yamazaki

31. Numbers from H1 and ZEUS, e and m ICHEP2006 results from ZEUS / Y. Yamazaki

32. Acceptance comparison btw. H1 and ZEUS … an outcome from the “HERA exotic combined working group” • ZEUS and H1 efficiency similar in the overlapped region • Most of the H1 events are in the ZEUS acceptance • ZEUS will try extending the acceptance to the smaller angle (forward) ICHEP2006 results from ZEUS / Y. Yamazaki

33. Acceptance comparison in pTX • ZEUS smaller than H1 slightly because of the angular cuts • Flat in pTX ICHEP2006 results from ZEUS / Y. Yamazaki

34. Summary • Finalising the HERA-I analysis • Focus is moving to HERA-IIZEUS is excited about large luminosityHoping for successful e+ running ICHEP2006 results from ZEUS / Y. Yamazaki