A Search for Excited Quark Production at H1 Andrew Rimmer IoP Conference University of Liverpool 1 March 2005 Contents of talk Introduction to HERA and H1 Phenomenology of excited quarks Event selections Control distributions Final distributions Some results Conclusions IoP Conference 2 March 2005 Centre of mass energy = 320 GeV IoP Conference 3 March 2005 The H1 Detector IoP Conference 4 March 2005 Compositeness and Excited Quarks Many BSM theories predict a new layer of substructure: Quarks and Leptons as composite particles? This could lead to excited states of SM particles HERA is an ideal place to look for these IoP Conference 5 March 2005 Phenomenology of Excited Quarks Lagrangian models the interactions of excited quarks with SM particles: ⎡ τ a λa ⎤ = 1 *σ μν a + ′ ′ Y + a + Lint FR ⎢gf Wμν g f Bμν gs fs Gμν ⎥FL h.c. 2Λ ⎣ 2 2 2 ⎦ Λ is the compositeness scale ′ f , f and fs are form factors, allowing arbitrary couplings to the SM gauge groups IoP Conference 6 March 2005 Production is possible at HERA via electroweak coupling at low Q2 Look for photon, W and Z decays. Tevatron has better handle on gluons. Assume that fs= 0 to prevent gluon couplings from dominating IoP Conference 7 March 2005 Currently concentrating on decay to Jet + Photon. This is possible in s-channel and u-channel at H1. IoP Conference 8 March 2005 Outline of analysis Event selection 2 level selection: 1) Loose selection: - Control distributions 2) Tight final selection: - Final plots - Efficiencies and limits IoP Conference 9 March 2005 Main pre-selection cuts At least 1 photon/electron Elec Pt > 10 GeV At least 1 Jet Jet Pt >10 GeV Cut out inefficient regions of detector Background rejection using topological filters IoP Conference 10 March 2005 IoP Conference 11 March 2005 IoP Conference 12 March 2005 Main final selection cuts Photon Pt > 20 Gev Jet Pt > 20 GeV Jet Theta < 90 degrees Photon Theta < 90 degrees Jet and Photon back to back in r-phi No track linked to the photon within 20cm, except for theta < 25 degrees Invariant Mass > 50 GeV IoP Conference 13 March 2005 IoP Conference 14 March 2005 Jet + photon data candidate IoP Conference 15 March 2005 95 % confidence level limits were calculated on the Cross section * branching ratio of q* Æ q + photon Statistical and systematic errors taken into account qÆ q + gamma IoP Conference 16 March 2005 Conclusions No evidence for q* seen in 99-00 data Limits on cross sections calculated Still to do Calculate limits on the coupling (f / lambda) Look at other q* decay channels IoP Conference 17 March 2005 Selection Efficiencies for Jet + Photon channel Mass 50 75 100 125 150 175 200 225 250 275 300 (GeV) Eff (this 0 39 44 49 53 55 56 58 59 59 58 analysis) Eff (94-97 22 33 36 -- 42 -- 41 -- 40 -- -- analysis) IoP Conference 18 March 2005.