Search for New Physics at HERA

Transcription

1 Search for New Physics at HERA Andrea Parenti (DESY) for the H and ZEUS collaborations CIPANP 009 S. Diego, 8/05/009

2 Outline Introduction to HERA Model dependent searches Quark radius Excited fermions Leptoquarks Single top production Model independent searches Isolated lepton final states Multi-lepton final states General searches CIPANP09 A. Parenti

3 The HERA Collider The world only ep collider, in DESY Hamburg Center-of-mass energy: up to 30 GeV Two colliding, general purpose experiments, H and ZEUS Operations ended in Jun 007 Collected luminosity: HERA I, : ~0. fb /exp HERA II, : ~0.4 fb /exp (with polarized e ± beams) CIPANP09 A. Parenti 3

4 Deep Inelastic Scattering at HERA HERA investigates ep collisions e + k=(e e,p e ) x P q k e + / ν e X q (pb/gev dσ/dq HERA I & II ) + H e p NC (prel.) - H e p NC (prel.) + ZEUS e p NC (prel.) - ZEUS e p NC SM e p NC (HERAPDF 0.) - SM e p NC (HERAPDF 0.) p P=(E p,p p ) Q = -q gives the resolving power of the EW probe New physics would appear at high-q, ie small distance: at HERA down to 8 m X p CIPANP09 A. Parenti H e p CC (prel.) - H e p CC 005 (prel.) + ZEUS e p CC (prel.) - ZEUS e p CC SM e p CC (HERAPDF 0.) - SM e p CC (HERAPDF 0.) y < 0.9 P e = Q (GeV ).

5 Quark Radius Hprelim-074 ZEUS-prel A decrease in the cross section at high-q is expected if quarks are not pointlike: ZEUS N/N CTEQ5D ZEUS (prel.) e ± p R q = (0.6 6 cm) R q = -(0.8 6 cm) No deviation from SM limits are set on R q (95% CL): ZEUS: R q < 0.6* -3 fm Quark Radius Limits (prel.) H: R q < 0.74* -3 fm 3 4 Q (GeV ) With a similar fit we can also look for contact interactions ( backup slides) CIPANP09 A. Parenti 5

6 Excited Fermions () arxiv: Phys.Lett.B666:3 Phys.Lett.B663:38 Excited fermions would be signature of compositeness Compositeness could explain 3 families and mass hierarchy Excitation/de-excitation described by effective Lagrangian: [f, f' and f s are the couplings to the SM gauge groups] Example: production and decay of e* CIPANP09 A. Parenti 6 Events Search for e* at HERA (475 pb ) H H Data All SM e* signal e* e γ (ela.) M eg e* Mass [GeV]

7 Excited Fermions () ] f / Λ [GeV H looked for all possible decay channels and did not find any deviation from SM limits were set on f/l (@ 95% CL) Search for e* at HERA (475 pb ) H f / Λ = / Me* Tevatron (0 pb ) LEP (direct) f = + f LEP (indirect) H e* Mass [GeV] ] f / Λ [GeV - -3 Search for ν* at HERA (e p, 84 pb ) H f/l limits can be translated into mass limits assuming f/l = /M f* L ν* Mass [GeV] CIPANP09 A. Parenti 7 - f = - f H f / Λ = / M ν* ] f / Λ [GeV M e* >7 GeV Search for q* at HERA (475 pb DELPHI BR(q* qγ)= H f = f, f s q* Mass [GeV] ) = 0 f / Λ = / Mq* M n* >3 GeV [assuming f=-f'] M q* >5 GeV [assuming f s =0] H

8 Leptoquarks () Hprelim-0764 LQs appear in many SM extensions Couple to both electrons and quarks and carry SU(3) color, fractional electric charge, baryon (B) and lepton (L) number Fermion number: F= 3B+L = 0, LQs model are explored in Buchmüller-Rückl-Wyler (BRW) framework (4 different LQ types) We search for LQ decaying into e-jet or n-jet: CIPANP09 A. Parenti 8

9 Leptoquarks () Full statistics analyzed by H (prel. results) Events / 0 GeV No deviation from SM, so limits on coupling are 95% CL 4 3 NC Leptoquark Search, HERA I+II H Data (prelim.) SM SM Uncertainty H e ± p (449 pb ) / GeV M LQ Events / 0 GeV 3 CC Leptoquark Search, HERA I+II H Data (prelim.) SM SM Uncertainty H e ± p (48 pb ) / GeV M LQ Leptoquark Search, HERA I+II (449 pb ) Leptoquark Search, HERA I+II (449 pb ) λ Excluded ~ + S /,L (e d) H prelim. single LQ F= λ Excluded - S 0,L (e u, νd) H prelim. single LQ HERA limits are complementary to LEP and Tevatron H (94-00) single LQ H (94-00) single LQ - D0 pair prod. D0 pair prod. - OPAL indir. limit L3 indir. limit CIPANP09 A. Parenti M LQ / GeV M LQ / GeV

10 Isolated Leptons arxiv: Phys.Lett.B67:6 Look for events with isolated, high-p T lepton (e, m), missing P T and hadronic system (P T X ) e + e + Events e,µ + P H SM production: ep miss T events at HERA (e + p, 9 pb ) H Data All SM Signal Events ew ± X (s~.3pb) 8 6 ZEUS PSfrag replacements miss Isolated e, µ + P + T ZEUS e p 96 pb SM MC non-w MC l q W + q ν l l X [GeV] P T X P T (GeV) In H e + p data, P T X >5 GeV: 7 obs / 8.0±.3 exp (.4s excess) No excess seen in e - p, also no excess observed by ZEUS CIPANP09 A. Parenti

11 PSfrag replacements Single Top production Produced in SM via CC interaction ep ntbx... but tiny cross section s = O(fb) BSM: production via Flavor Changing NC No significant excess in the signal region, limits are set on anomalous coupling k tug tuz V 0.8 u l + l p e U t κ tuγ Xp W + Limits on Single Top Quark Production via FCNC ZEUS arxiv: ZEUS-prel Λ = m top = 70 GeV e b H (474 pb ν, q l +, q ) Search for Single Top Quarks at HERA (474 pb ) Events Electron+Muon Channel Top Preselection without cut on lepton charge H H Data All SM ANOTOP CDF L3 Λ = m top = 75 GeV κ tcγ = V tcz = 0 New ZEUS prel k tug < 0.3 CIPANP09 0 A. Parenti lνb M [GeV] PSfrag replacements κ tuγ

12 Multi-Leptons Hprelim ZEUS-prel Look for events with or more isolated high-p T leptons (e,m) SM production via Bethe-Heitler process H and ZEUS combined results (0.94 fb ) e + e + l + l - Events 3 - Multi-Leptons at HERA (e + p, 0.56 fb ) H+ZEUS Data (prelim.) SM SM Pair Prod. +3 leptons Σ P T [GeV] HERA Exotics Working Group Events Data (prelim.) 3 SM SM Pair Prod. - - Multi-Leptons at HERA (e p, 0.38 fb ) H+ZEUS +3 leptons Σ P T [GeV] CIPANP09 A. Parenti HERA Exotics Working Group p In e + p data, SP T >0 GeV: 7 obs/.94±0.7 exp (excess of.6 s) In e - p data, SP T >0 GeV: 0 obs/.9±0. exp X p

13 General Searches Phys.Lett.B674:57 Look for events with isolated e, g, m, n, jets having P T >0 GeV Events are classified depending on the number and type of high-p T objects at least one event in 7 topologies In general good agreement with SM Deviation from SM is searched for in distributions of SP T and M all with a statistical algorithm CIPANP09 All deviations are compatible with statistical fluctuations A. Parenti

14 Summary HERA collected ~0.5fb per experiment Most analyses make use of the full statistics Overall good agreement with the SM: Exclusion limits are set, competitive to LEP and TEVATRON World's best limits on excited fermions, anomalous productions To reach the best sensitivity, H and ZEUS started combination CIPANP09 A. Parenti 4

15 Backup Slides

16 The H Detector CIPANP09 A. Parenti 6

17 The ZEUS Detector CIPANP09 A. Parenti 7

18 Contact Interactions () Phys.Lett.B568:35 ZEUS-prel Any interaction appearing at much higher energy than center-of-mass can be represented by an effective Lagrangian where L is the new physics scale Many models are possible, depending on the chiral structure assumed CIPANP09 A. Parenti 8

19 Contact Interactions () N/N CTEQ5D N/N CTEQ5D ZEUS Contact Interactions Limits (prel.) Contact Interactions Limits (prel.) 3 4 ZEUS e + p VV Λ = 8.0 TeV VV Λ + = 6.3 TeV ZEUS (prel.) e - p AA Λ = 6.7 TeV AA Λ + = 6. TeV Q (GeV ) Q (GeV ) No deviations from the SM. Limits are set on the scale L for each model: ZEUS (94-96): H (HERA I): L> TeV L> TeV CIPANP09 A. Parenti 9 VV AA VA X X X3 X4 X5 X6 U U U3 U4 U5 U6 LL LR RL RR ZEUS (prel.) e ± p 330 pb /Λ best fit value allowed ±/Λ range +/Λ best fit value Λ (TeV) Λ + (TeV) ±/Λ (TeV - )

20 Multi-Leptons Phys.Lett.B668:68 Events Look for events with or more isolated high-p T leptons (e,m) SM production via Bethe-Heitler process Both H and ZEUS have results with full statistics: H Data 3 All SM Pair Prod. ZEUS 480 pb +3 leptons Total SM - Multi-Leptons at HERA (e + p and e p, 463 pb ) - Events H [GeV] M (GeV) Σ P T ZEUS Events 3 - ZEUS NC DIS QEDC Di-τ l Σp T (GeV) e + e + CIPANP09 A. Parenti 0 p In H e + p data, SP T >0 GeV: 5 obs/0.96±0. exp l + l - X p No excess in e - p data No excess seen by ZEUS

21 arxiv: Search for t production Eur.Phys.J.C48:699 ZEUS-prel Events with an isolated, high-p T t, missing P T, hadronic system di-t events Events H H Data All SM Signal X [GeV] P T H analysis, P X T >5 GeV: obs /.5±0. exp ZEUS prelim (HERAII): obs / exp H (HERA I data): 30 obs / 7.±4. exp CIPANP09 A. Parenti