1 / 32

Recent Results from ep interactions at HERA

Recent Results from ep interactions at HERA. Alessandro Polini - INFN Bologna. on behalf of H1 and ZEUS Collaborations. Outline: HERA and the Experiments selection of results: Structure Functions, QCD fits,  s Heavy Flavour Production Hadron Spectroscopy: Pentaquarks

balin
Download Presentation

Recent Results from ep interactions at HERA

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Recent Results from ep interactions at HERA Alessandro Polini - INFN Bologna on behalf of H1 and ZEUS Collaborations • Outline: • HERA and the Experiments • selection of results: • Structure Functions, QCD fits, s • Heavy Flavour Production • Hadron Spectroscopy: Pentaquarks • Standard Model and New Physics • First Results from HERA II data • Outlook and Perspectives NEW TRENDS IN HIGH-ENERGY PHYSICS (experiment, phenomenology, theory) Yalta, Crimea, Ukraine, September 10-17 A. Polini

  2. The HERA e±p Collider : 920 GeV : 27.5 GeV ~ 6.3 km circumference Resolution: 10-18 m 50 TeV on fixed target A. Polini

  3. HERA I (1992-2000): 130 pb-1/experiment e-p ~20 pb-1, e+p ~110 pb-1 2001: Luminosity upgrade 2002/2003: Background problems 2004: Positrons 50 pb-1 /expt Aug05: Electrons ~120 pb-1 /expt Nov05/Jan06: Shutdown June 2007: Scheduled end of HERA Expect ~ 700 pb-1/expt by the end of HERA HERA II: 3-4 times higher luminosity Polarisation Luminosity at HERA 50% Polarisation (%) A. Polini

  4. ep scattering at HERA √s = 300-318 GeV (Energy C.M.) W= M*p (Hadronic Energy) Q2= -q2 (Photon Virtuality) x = Bjorken x (energy carried by the struck parton in the proton) Photoproduction: Q2~0 (1<GeV2) - Real Photon-Proton Scattering Deep inelastic Scattering (Q2>1 GeV2) - *probing the proton structure - At High Q2 ~ M(Z0) weak contributions Z0,W± becoming relevant A. Polini

  5. Charged and Neutral Currents Neutral Current e+ p  e+X Neutral Currents Charged Current e+p  X Charged Currents A. Polini

  6. Structure Functions F2(x,Q2) F2 vs. Q2 Data span 4 orders of magnitude in Q2 Positive/negative scaling violations SM gives excellent description  F2 vs. x Steep rise of F2 as x 0 No slow down in the rise of F2 seen yet A. Polini

  7. The Structure of the Proton HERA QCD fits: • Precise determination of the parton density functions • High-x parton distributions require extra constrains (fixed target experiments… ) • H1 and ZEUS fits: reduce corrections and systematics when using only HERA data. • Overall still space for improvement of statistical errors with higher luminosity • HERA II: even more accurate determination of all proton PDFs within a single experiment A. Polini

  8. Quark Sea and Gluon Density Sea and Gluon density well determined at low-x (x<10-2) The sea distribution rises at low-x for all Q2 The gluon density becomes valence-like at low Q2 Sizeable reduction of the gluon uncertainty at mid x in by the use of the jet data (jet in DIS, di-jet in PHP) Precise PDFs extraction from HERA data over the full x,Q2 range with minimal external input A. Polini

  9. 10-1 10-1 10-1 10-1 x Structure Function xF3 xF3 constrains uv dv at high x A. Polini

  10. Neutral Cross Section at very high x • Q2 reconstructed from the scattered electron • If jet inside detector: x from Ejetjet • If jet outside: take integral x<1 (last bin) • Extend to x > 0.4 A. Polini

  11. Summary of s Measurements HERA: • Many different and precise measurements of s • HERA experiments doing precision Jet Physics (ssyst down to 2%): • Data clearly show the running of s (GeV) A. Polini

  12. Heavy Quark Production Production mechanism dominated by Boson–Gluon-Fusion The heavy mass provides the hard scale for pQCD applicability - gP: Q2 < 1GeV Hard scales: mb, pT • DIS: Q2 > 1GeV2 Hard scales: mb, Q2, pT Beauty semileptonic decay (m). Two independent observables: • Large B mass: pTrel of m relative to jet axis • Large B lifetime: m impact parameter d MC simulation for uds, c, and b contributions Significance d/(d) A. Polini

  13. Beauty in Photoproduction and DIS • Wide range of beauty cross section measurements from semileptonic decay in Photoproduction and DIS • 2 independent beauty observables , pTrel • General agreement between Data and NLO QCD both in Photoproduction and DIS • DIS A. Polini

  14. Measurement of F2cc F2bb at high Q2 Quark fractions • H1: New inclusive measurements of c and b production at high and low Q2 • Higher statistics compared to exclusive (,D*) analyses • First extraction of b contribution to F2 • Use inclusive impact parameter method for all events with tracks precisely measured by the silicon tracker • Measurements in agreement with H1 PDFs and ZEUS F2cc (D*) A. Polini

  15. Relevance for LHC Low x PDF: only measured at HERA Small x up to 10-4 important for 100 GeV < M < 1 TeV central region at LHC High x PDF: Q2 evolution to ~104 GeV2 QCD still works: prediction power HERA provides LHC with crucial input for signal cross section and QCD background estimation. QCD evolution Ref: HERA-LHC WS A. Polini

  16. Q0c uuddc  D*p Hadron Spectroscopy: Pentaquarks • q+(1530): • proposed by Diakonov, Petrov, Polyakov in 1997: • prediction of Mass ~ 1530 MeV,  < 15 MeV • Observation: • many positive results from experiments (incl. ZEUS) • Still to clarify mass and width • preliminary production cross-section • production ratio vs (1520) • X-- (1860): not confirmed by any experiments but NA49 (but it should be there if pentaquark isotensor q+ exists…) • q0c (3100): seen by H1, but not by ZEUS • Predictions: • Jaffe-Wilczek, Wu-Ma (lower mass) • Karliner-Lipkin, Cheung A. Polini

  17. ZEUS: Search for q+ p K0s / q- p K0s _ ZEUS: 121pb-1, DIS. Identify K0s +-; p, p: identify by dE/dx Signal seen in both charges - pK0santipentaquark? + Cross section (Q2>20 GeV): vis = 125 ± 27 (stat) pb +/ production ratio vs Q2min~ 4%, + production rate higher pronounced at >0 (forward). + not observed by H1 (although result not incompatible)  - A. Polini

  18. Search for NA49 signal (--) at ZEUS ZEUS: • Analysis similar to NA49 using DIS data • higher statistics & smaller background • Clean Ξ0 (1530) signal though No pentaquark signal observed A. Polini

  19. Search for charmed PQ, c D*p, in H1 D0s k H1 96-00 75 pb-1 Background + signal hypothesis fit: Background only hypothesis: Nb=51.7±2.7 Background fluctuation probability: 4x10-8 (Poisson)= 5.4  (Gauss) Independent confirmation: Signal observed also in Photoproduction Studies on (D*p/D*)  and xobs different production mechanism But ZEUS: - DIS D* sample 1995-2000, 125 pb-1, Q2>1 GeV2 ~9700 D* - No evidence for a signal at 3.1 GeV both in DIS and PHP A. Polini

  20. Standard Model and E-W parameters Light Quark couplings to Z boson From H1 PDF fits including additional EW parameters Mprop82.87 ± 1.82 exp GeV W mass value fit: MW= 80.786 ± 0.205 exp GeV + the world average MZ indirect determination of sin2W=1-M2W/M2Z=0.2151 ± 0.0040 exp Top quark mass: mt=104 ± 44exp GeV First determination in DIS at EW scale A. Polini

  21. LQ: Boson with baryonic and leptonic quantum numbers Fermion Number F=3B+L HERA (LQ single production): s-channel eq fusion resonance in eq (νq) invariant mass in NC (CC) events Ecm< 300 GeV Resonant States (F=0 in e+p, F=2 e-p) Ecm>>300 GeV Contact Interactions TEVATRON: LQ pair production LEP2: virtual in e+e-hadrons No excess found in any channel Search for Leptoquarks A. Polini

  22. HERA II A. Polini

  23. HERA II: D* production A. Polini

  24. Charged Currents First polarised CC cross section measurements including 2005 data. SM expectation: σ±(Pe) = (1± Pe ) σ±(Pe=0) Right-handed currents are absent A. Polini

  25. HERA 2007 HERA II: Neutral Currents • Ratio of polarised cross sections • No conclusive observation yet of effect of longitudinal polarisation on cross sections • Consistent with SM. • Precision statistically limited • HERA II will provide O(1 fb-1) A. Polini

  26. Still H1 excess in e,μ channel Update HERA II data (74 pb-1eP): 6 new electron events with pT(had) > 25 GeV no new muon event Events with isolated lepton and missing transverse momentum Dominant SM process: on-shell W production (σ~1pb)  search: • H1: no excess seen (HERA I only) • Small excess in ZEUS (HERA I) A. Polini

  27. Conclusions and Outlook New results completing the picture from HERA I: • HERA: a unique powerful and versatile QCD probe • QCD results on structure functions, PDFs and αS more and more precise • HERA is not just a QCD machine (many more searches and results not shown) • Important contributions to SM and beyond Great expectations from HERA II data • High luminosity & polarized e± beam • Improved detectors (Tracking, Silicon, Trigger) • Higher luminosity will clarify some open issues • HERA II running till mid 2007 (expect 700 pb-1) A. Polini

  28. The End A. Polini

  29. The H1 detector A. Polini

  30. 107 Hz CTD Front End CAL Front End Other Components CAL FLT CTD FLT ~0.7 s 5s pipeline 5s pipeline Global First Level Trigger 500Hz GSLT Accept/Reject Other Components CAL SLT CTD SLT Event Buffers Event Buffers ~10 ms Global Second Level Trigger GSLT Accept/Reject 40Hz CAL CTD Event Builder Third Level Trigger cpu cpu cpu cpu cpu cpu 5Hz Offline Tape The ZEUS Detector A. Polini

  31. Are quarks “elementary”? • Form factor measurement at Q2 ~ 40000 GeV2 • Resolution 1/Q ~ 10-16cm = 0.001 proton radius • Compare measured to expected cross section • Limits on quark size • H1: Rq < 1.0 x10-16cm • ZEUS: Rq < 0.85 x10-16cm A. Polini

  32. Global vs ZEUS/H1 fit A. Polini

More Related