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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
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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
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
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
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
Charged and Neutral Currents Neutral Current e+ p e+X Neutral Currents Charged Current e+p X Charged Currents A. Polini
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
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
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
10-1 10-1 10-1 10-1 x Structure Function xF3 xF3 constrains uv dv at high x A. Polini
Neutral Cross Section at very high x • Q2 reconstructed from the scattered electron • If jet inside detector: x from Ejetjet • If jet outside: take integral x<1 (last bin) • Extend to x > 0.4 A. Polini
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
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
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
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
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
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
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
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
Search for charmed PQ, c D*p, in H1 D0s 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
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 sin2W=1-M2W/M2Z=0.2151 ± 0.0040 exp Top quark mass: mt=104 ± 44exp GeV First determination in DIS at EW scale A. Polini
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
HERA II A. Polini
HERA II: D* production A. Polini
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
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
Still H1 excess in e,μ channel Update HERA II data (74 pb-1eP): 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
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
The End A. Polini
The H1 detector A. Polini
107 Hz CTD Front End CAL Front End Other Components CAL FLT CTD FLT ~0.7 s 5s pipeline 5s 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
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
Global vs ZEUS/H1 fit A. Polini