HEP2008-OlympiaTh. D. Papadopoulou1 Neda, the unique river with a feminine name ! Theodora D. Papadopoulou ( coming from the highland of Olympia…) NTU Athens H1 Collaboration Hellenic HEP Olympia - April 17, 2008

HEP2008-OlympiaTh. D. Papadopoulou2 H1, Z.Phys. C74 (1997)191 ZEUS, Z.Phys. C74(1997)207 Do we have surprises from HERA nowadays ?

HEP2008-OlympiaTh. D. Papadopoulou3 Outline  HERA I + HERA II  CC and NC Cross section measurements  Quark form factor  Contact Interactions  Leptoquarks & LFV  Search for SUSY quarks  Isolated Leptons with P( Τ )-missing  Multi-lepton search  HERA to LHC physics  Outlook - As an Epilogue

HEP2008-OlympiaTh. D. Papadopoulou4 HERA II: ep collisions with e - /e + polarisation Detector and Luminosity upgrade large backgrounds identified and overcome in 2002/ 03 efficient data taking since 10/ 03 HERA operated until 1 July 2007 polarized e - /e + beam with spin rotators

HEP2008-OlympiaTh. D. Papadopoulou5 HERA I / HERA II World’s unique e p Accelerator and Collider Operated H1 & ZEUS each have collected 0.5 fb־¹ of high quality Physics data balanced in e± 72 % of the Luminosity is from HERA II longitudinally polarized e± beams Polarization typically 30 – 40 %

HEP2008-OlympiaTh. D. Papadopoulou6 Searches for new currents affecting the DIS process  Deep Inelastic Scattering precision experiments Measure E’ e, θ e, E h, θ h  [ 0.3 –1% ; 0.2-1mrad; 1-2%, 1-2mrad ]  reconstruct x, Q 2 : kinematics is overconstrained Highly Efficient 4π Detectors (Calorimeters, Chambers in solenoid field) Accurate run vertex (upgrade) (drift chambers: 200 μm and Si trackers: 20 μm resolution ) Luminosity from Bethe-Heitler scattering [ ep  epγ ] theoretical error ~ 0.5 % HERA I lum. error was 1.5 % HERA II lum error in average was 3.5 % HERA II

HEP2008-OlympiaTh. D. Papadopoulou7 Cross section measurements with HERA  DIS is the golden process to study the structure of matter (and at HERA the structure of proton) Measurements up to ~ Q 2 Electroweak Unification N C C

HEP2008-OlympiaTh. D. Papadopoulou8 Quark radius limit Quarks are pointlike down to proton radius/1000 H1 : < m ZEUS: < m

HEP2008-OlympiaTh. D. Papadopoulou9 CC polarised cross sections (HERA II) Total CC cross section (Q 2 > 400 GeV, y < 0.9 ) vs. polarisation  H1 and ZEUS measurements consistent with SM  no right handed CC limit on right-handed W : M(W R ) > 208 GeV CDF limit : M(WR ) > 790 GeV Extrapolation to P = ± 1 in SM σ (RH) =0 for electrons and σ (LH) =0 for positrons and the total cross-section changes linearly with polarisation.  nonexistence of RH currents within the framework of SM.

HEP2008-OlympiaTh. D. Papadopoulou10 Contact Interactions Parametrisation of new physics due to composite fermions or New heavy mediators ( m X >> ) Λ is the energy scale of new physics Limits on ε Λ:  Similar sensitivity achieved at Tevatron Limits set by looking for deviations from SM limits Λ +, Λ -, correspond to constructive, destructive interference with SM (g 2 = 4π, ZEUS ZEUS: Λ > 2.0 – 8.0 TeV H1 : Λ > 1.6 – 5.5 TeV at 95% CL data

HEP2008-OlympiaTh. D. Papadopoulou11 Leptoquarks b e ( μ ) LQ s μ ( e )

HEP2008-OlympiaTh. D. Papadopoulou12 Leptoquarks at HERA ep is the golden machine to study LQs SEARCH FOR 1 rst GENERATION LQs BRW Model

HEP2008-OlympiaTh. D. Papadopoulou13 LQ existing Bounds From EPS-2003, A. Zarnecki SCALAR LQs WITH F=0 H1 (94-00) e + p H1 Coll. Phys. Lett B629(2005)9  for λ ~ 0.3 mass exclusion ~ 275 – 325GeV depending on LQ type Similar limits obtained by ZEUS  HERA limits beyond LEP & Tevatron

HEP2008-OlympiaTh. D. Papadopoulou14 LQ data analysis H1 ( ) data

HEP2008-OlympiaTh. D. Papadopoulou15 LQ data analysis HERA I + HERA II Data consistent with SM All H1 / HERA I + II e + p and e - p data from I. Panagoulias’ talk at DIS2008 – work on PhD / NTUA NC CC

HEP2008-OlympiaTh. D. Papadopoulou16 LQ Exclusion Limits -- comparison with LEP and Tevatron HERA extends the exclusion region from I. Panagoulias’ talk at DIS2008 – work on PhD / NTUA

HEP2008-OlympiaTh. D. Papadopoulou17 Search for Lepton Flavor Violation Limits on Yukawa Coupling assuming λ eq = λ μq I. Panagoulias, NTUA DIS08 e p  μ Χ 2 events seen/ 2.2 ± 0.6 expected

HEP2008-OlympiaTh. D. Papadopoulou18 R-parity Violation What is Rp and why go beyond ?  a discrete multiplicative symmetry in SUSY models connected to matter parity R p = 1 for SM particles R p = -1 for SUSY particles o SUSY particles produced in pairs o LSP is stable o experimental signature of SUSY E T miss fast proton decay is suppressed

HEP2008-OlympiaTh. D. Papadopoulou19 RpV Superpotential R p can be explicitly broken by trilinear terms in the superpotential o single sparticle production via a ΔL 0 or a ΔB 0 operator o Unstable LSP ! fast proton decay is suppressed if Lepton and Baryon number Violating Couplings not simultaneously present 9 Couplings 27 Couplings9 Couplings HERA Resonant squark production at HERA l +( l ) + multijets

HEP2008-OlympiaTh. D. Papadopoulou20 Beyond minimal LQs: SUSY quarks H1 data : 64.3 pb -1, 13.5 pb -1 e - p H1 Coll. EPJ C36 (2004) 495 : all squark types all decay modes  For λ’ = 0.3 ( λ’ 2 / 4π = α em ) squarks can be ruled out up to ~ 270 – 280 GeV Constraints within the MSSM

HEP2008-OlympiaTh. D. Papadopoulou21 Isolated leptons + P T miss events

HEP2008-OlympiaTh. D. Papadopoulou22 Isolated leptons : Results H1 e + p dataH1 e - p data H1 excess only appears in e + p data Fluctuations?(3.4σ) New Physics? No new events on 2005 e - p events with ΣΕ Τ >100 GeV The excess had to be clarified with the full HERA II data sets

HEP2008-OlympiaTh. D. Papadopoulou23 Isolated leptons : Results HERA I + II H1 e + p dataH1 e - p data All H1 / HERA I + II data : 478 pb -1 Events at high P T X also observed in latest data Different observations in e + p and e - p data ZEUS : Agreement with SM expectations σ ~ 1.3 pb but expect small P T X SM W  e, μ production

HEP2008-OlympiaTh. D. Papadopoulou24 Isolated leptons : H1 and ZEUS Combined Results H1 and ZEUS combined in a common phase space Total luminosity : fb -1 Good agreement with the SM Fluctuation in e + p for P T X > 25 GeV is reduced to 1.8 σ

HEP2008-OlympiaTh. D. Papadopoulou25 Multi-lepton Events ( e, μ ) All H1/ HERA I + II data with total luminosity : 459 pb -1 look for events with at least 2 isolated high P T leptons (e, μ) Topologies : ee, eμ, μμ, eee, eμμ Interesting events observed for Σp Τ > 100 GeV H1 in e + p : Data/MC = 4 / 1.2 ± 0.2 events ZEUS : good Data/MC agreement with multi-electrons Low SM background mainly produced via γγ scattering BUT waiting for ZEUS multi-muons VERY narrow possible surprise ?

HEP2008-OlympiaTh. D. Papadopoulou26 Multi-lepton events : H1 and ZEUS Combined Results H1 and ZEUS combined in a common phase space Total luminosity : fb -1 Few high P Τ events observed mainly in e + p for luminosity 0.56 fb -1 : Data/SM = 5 / 1.82 ±0.21 events

HEP2008-OlympiaTh. D. Papadopoulou27 HERA to LHC low x physics at HERA : PDFs  forward at LHC medium x physics at HERA  plateau region at LHC

HEP2008-OlympiaTh. D. Papadopoulou28 Kinematic Range  Dominant Contribution  Contributes when Q 2 ~ M 2 Z  Contributes only at high y  HERA PDFs extrapolate into the LHC region and their accurate determination are crucial to New Physics measurements at the LHC such as compactified extra dimensions and contact int.

HEP2008-OlympiaTh. D. Papadopoulou29 Triumph of pQCD !  The accurate measurements of HERA II especially on the F 2, F L structure functions, the low-x PDFs and the high-x gluon PDF are VERY important for the LHC DISCOVERY POTENTIAL ! New HERA-I PDF fit predictions vs H1/ZEUS combined data for NC e + p on PDF fit

HEP2008-OlympiaTh. D. Papadopoulou30 Direct Measurement of F L x – averaged F L as a function of Q 2 : consistent with QCD prediction FIRST PRELIMINARY

HEP2008-OlympiaTh. D. Papadopoulou31 HERA to LHC “Physics with HERA will be of much use when the physics at LHC becomes real.” Max Klein Hadron Collider Physics Conference July 2005

HEP2008-OlympiaTh. D. Papadopoulou32 Outlook HERA II run ended on July 1, 2007 with L ~ 1 fb -1 for both experiments H1 and ZEUS Combined analyses are underway towards the final results Results from HERA experiments are consistent and in good agreement with each other : It is a triumph of pQCD ! No evidence for New Physics at HERA ( No significant excess) Important contribution of HERA results to LHC physics

HEP2008-OlympiaTh. D. Papadopoulou33 LEP2 HERA Tevatron LHC ILC Desert ? New Physics ?

HEP2008-OlympiaTh. D. Papadopoulou34 Backup Slides

HEP2008-OlympiaTh. D. Papadopoulou35 Polarised Cross-sections  After the upgrade, HERA provides the experiments with longitudinally polarised lepton beams  The transverse polarisation builds up naturally (Sokolov-Termov effect)  Spin rotators flip the polarisation by 90º just before the lepton beam enters the interaction regions of experiments  Typical level of polarisation is ~ 40 % Polarisation : In SM σ (RH) =0 for electrons and σ (LH) =0 for positrons and the total cross-section changes linearly with polarisation.  nonexistence of RH currents within the framework of SM.

HEP2008-OlympiaTh. D. Papadopoulou36 D * p resonance in 3 GeV region- Pentaquark Katja Kruge talk – DIS08

HEP2008-OlympiaTh. D. Papadopoulou37 K. Kruge- DIS08

HEP2008-OlympiaTh. D. Papadopoulou38 K. Kruge- DIS08