html5-img
1 / 40

Hidden Valley

Hidden Valley. Vanya BELYAEV. Hidden Valley (Reminder). It is a class of phenomenological models which appears to be consistent with data and well motivated arises in many models, including string-theory constructions

starr
Télécharger la présentation

Hidden Valley

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. Hidden Valley Vanya BELYAEV

  2. Hidden Valley (Reminder) • It is a class of phenomenological models which • appears to be consistent with data and well motivated • arises in many models, including string-theory constructions • appears to be consistent with most methods for solving the hierarchy problem (supersymmetry, little Higgs models, TeV-extra dimensions, Randall-Sundrum scenarios) • Generic signals Vanya BELYAEV

  3. References hep-ph/0604261 • “Echoes of Hidden Valley at Hadron Colliders” by Matthew J.Strassler & Kathryn M.Zurek hep-ph/0605193 • “Discovering the Higgs through Highly-Displaced Vertices” by Matthew J.Strassler & Kathryn M.Zurek Vanya BELYAEV

  4. Hidden Valley • Extend the SM gauge group GSM with non-abelian group Gv • All SM particles are neutral with respect to Gv • There exist light particles (v-particles), charged under Gv and neutral under GSM • High dimension operators at TeV scale (induces by Z’ or by loops of heavy particles, carrying both GSM and Gv charges) allow interactions between SM and new particles Vanya BELYAEV

  5. Hidden Valley • In confining Hidden Valley model all v-particles assemble themselves into Gv-neutral “v-hadrons” • Some v-hadrons can decay (through high-dimension operators) into gauge-invariant combinations of SM-particles, with observable lifetimes (from zero to infinity) Vanya BELYAEV

  6. Hidden Valley: typical features I • There are several long-lived v-hadrons, with masses typically of the order v-confinement scale Lv • Some v-hadrons may be stable, providing dark matter candidates and missing energy signals, while others decay to neutral combinations of SM particles • Decay lifetimes can vary over many orders of magnitude; v-hadrons can decay promptly or produce a displaced vertex anywhere in the detector or decay outside the detector Vanya BELYAEV

  7. Hidden Valley: typical features II • Some v-hadrons decay predominantly to heavy flavour, while others decay more democratically into fermion-antifermion final states or fermion-antifermion plus another v-hadron; other final states can include two or three gluons, WW or ZZ • V-hadron production multiplicities at LHC could be large, if Lv «1 TeV Vanya BELYAEV

  8. Hidden Valley: scenarios • M.S. & K.Z. consider the following base scenario • A simple v-Model Vanya BELYAEV

  9. 2 regimes • Two flavour regime • mU ~ mC « Lv • “QCD-like” • One flavour regime • mC » Lv » mU Vanya BELYAEV

  10. Existing Limits • Cosmological constraints are minimal • LEP-I could constrain M(Z’)/g’ > 10 TeV with easy-detectable v-hadrons: • s(LHC@m(Z’)=2.5 TeV, g’=0.25)~20fb • in 2LF regime • Z → v-p0 v-p0 forbidden • Z → v-p+ v-p- invisible • Z → v-p+ v-p- v-p0 has 10 times smaller Br v-p0 & v-p± are neutral! Q=0 Vanya BELYAEV

  11. Production • V-quark production result in multiple v-hadron production with ratio m(Z’)/Lv determining the average multiplicity and whether the event v-hadrons are distributed spherically, in two collimated v-jets or something in between • For 2LF regime the dominant signal is multiple b-jet pairs (from v-p0) plus missing energy (from invisible v-p+) • For 1LF regime more lepton pairs (from wv,sv,…) Vanya BELYAEV

  12. Production Vanya BELYAEV

  13. Higgs Mixing & Glueballs • Higgs Mixing results in gg→h→QQ • unaffected by LEP constraints • Increase the production rate of v-hadrons • Though rare such decays could have a good signature against the background • In the case of LHCb they are effectively enhanced due to acceptance • In the regime mU,mC » Lv many stable glueballs appear Vanya BELYAEV

  14. Production Vanya BELYAEV

  15. Hidden Valley Production v-p0 v-p0 v-p+ Vanya BELYAEV

  16. Hidden Valley Production • All events have been produced • Partly on Syracuse Linux cluster • Many thanks to JC and Steve for the kind help • The first analysis steps: • Efficiencies for the standard L0 trigger & the different trigger lines : • Ecal: e,p0,g • Muon: m&2m • Hcal • The rates after L0 • High Level Trigger • Jets reconstruction • (Background?) Vanya BELYAEV

  17. The standard L0 efficiency m(v-p0)=120 GeV/c2,t(v-p0)=0.1 ps, t(v-p+)=10 ps m(v-p0)=70 GeV/c2,t(v-p0)=1 ps, t(v-p+)=∞ m(v-p0)=50 GeV/c2,t(v-p0)=10 ps, t(v-p+)=∞ m(v-p0)=35 GeV/c2,t(v-p0)=100 ps, t(v-p+)=∞ M(H)=180 GeV/c2, m(v-p)=70 GeV/c2 , t(v-p)=1 ps M(H)=180 GeV/c2, m(v-p)=50 GeV/c2 , t(v-p)=10 ps M(H)=180 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=100 ps M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=100 ps M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=10 ps M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=1 ps Vanya BELYAEV

  18. L0 efficiency • L0 efficiency is enormously high: 75-90% • In accordance with the expectations from very hard generator spectra: • L0 Ecal : Electron, Photon, Local p0 and global p0) • L0 Hcal • Good surprise: High L0 Muon efficiency ~40% • Muon efficiency “almost” independent on lifetime, slightly depends on masses, no large difference between Higgs and non-Higgs variants • Calorimeter efficiency does depend on masses, lifetimes and Higgs/non-Higgs Vanya BELYAEV

  19. Important note: • All Calorimeter triggers saturates at 5 GeV of transverse energy • 1 “calorimeter” candidate (2x2 cluster) per board, saturated at 5 GeV of ET • Each cell is saturated at 10-12 GeV of ET • There exist one “global” quantity : non-saturated sum of ET of all saturated candidates • Characterize the overall event activity • Together with (practically useless) pileup veto and Spd-multiplicity veto Vanya BELYAEV

  20. “Sum-ET (pseudo)alley” • The large fraction of signal L0 accepted events will be picked up with the standard L0-confirmation alleys: muon, di-muon, muon-hadron, hadron, electron, (di-electron),… • It is definitely true for small lifetime O(1cm) and the prompt decay • Not clear if it is true for large (>20 cm) lifetimes • To be verified, some HLT code available • For a moment try to rely only on general features: event activity: “Sum-ET (pseudo)alley”: • Select L0 events with Sum-ET > threshold • The simplest possible alley: no action at all! • Check minbias rate versus efficiency for various thresholds Vanya BELYAEV

  21. Sum-Et cut for L0 accepted events: Higgs Signal Efficiency m(H)=180 GeV m(H)=120 GeV 1MHz: farm input Minbias Rate [MHz] Minbias Rate [MHz] 10kHz: “typical” L0-confirmation alley Vanya BELYAEV

  22. Sum-Et cut for L0 accepted events: multi-vp m(v-p0)=120 GeV/c2,t(v-p0)=0.1 ps, t(v-p+)=10 ps Signal Efficiency m(v-p0)=70 GeV/c2,t(v-p0)=1 ps, t(v-p+)=∞ m(v-p0)=50 GeV/c2,t(v-p0)=10 ps, t(v-p+)=∞ m(v-p0)=35 GeV/c2,t(v-p0)=100 ps, t(v-p+)=∞ 1MHz: farm input Minbias Rate [MHz] 10kHz: “typical” L0-confirmation alley Vanya BELYAEV

  23. Sum-Et pseudo-alley • It is possible to achive 10kHz minbias rate (102 rejection) keeping 25-45 % of efficiency for the signal • For Higgs: efficiency depends only on vp masses • For multi-vp efficiency also related to the mass • + some efficicnecy from the standard alleys • Expect LARGE contribution for small lifetimes and prompt decays • Next step: Jet-finding • Full event recontruction • at 10kHz one can run jet-finding algorithm Vanya BELYAEV

  24. Fast Jet finding at HLT • Standard kT-Jet algorithm • “Fast kT-Jet” – the same physics, but another quite tricky reimplementation using the sophisticates geometrical & topological reformulation of the jet-finding procedure in the terms of Voronoi diagram and Delaunay triangulation • Marco Cacciary & Gavin P. Salam hep/ph-0512210 • No O(N3) dependency: ~order of magnitude faster in our case Vanya BELYAEV

  25. Jet finding • Use LoKi/LoKiJets package • Input • all reconstructed long tracks • all reconstructed photons • clusters in Ecal, not matched with any reconstructed track, including T-track. Probably there is some inconsistency here. • Different from ATLAS/CMS approach • Standard kT-jet algorithm • “R-parameter” = 0.7 • NB: it is “C++-R”, it is different from “FORTRAN-R” • Close to the optimal for many aspects • (Victor Coco, Laurant Locatelly, V.B. ) Vanya BELYAEV

  26. Jet angular resolution Df and Dh in between the reconstructed jet and the nearest b-quark Df Dh b-quark before fragmentation Vanya BELYAEV

  27. Jet angular resolution b-quark before fragmentation Dh Df Vanya BELYAEV

  28. Jet Energy/pT resolution • So far so good with jet angular resolution • The situation with energy resolution is unclear • There are many reasons why e(jet) ≠ e(b) • Missing particles: neutrinos, KL, neutrons,… • Extra particles: pile-up & jets overlap,… • Overlap of photons with the charged tracks • Detector inefficiencies and acceptance • Calorimeter saturation • Reconstruction artefacts: ghosts • Jet finding procedure • Choice for the recombination schema, parton mass, etc. Jet-energy needs to be calibrated Vanya BELYAEV

  29. Jet energy correction pT(b)/pT(jet) [GeV/c] pT(jet) Vanya BELYAEV

  30. Problem: m(v-p0)=120 GeV/c2,t(v-p0)=0.1 ps, t(v-p+)=10 ps pT(b)/pT(jet) m(v-p0)=70 GeV/c2,t(v-p0)=1 ps, t(v-p+)=∞ m(v-p0)=50 GeV/c2,t(v-p0)=10 ps, t(v-p+)=∞ m(v-p0)=35 GeV/c2,t(v-p0)=100 ps, t(v-p+)=∞ [GeV/c] pT(jet) Vanya BELYAEV

  31. Problem: • Naïve assumption that energy correction is the function of pT(jet) only is wrong • Have been blindly used for H→2b with small acceptance (h) corrections • Correction function does depend on other parameters … • What to do??? • For the time being: rescale the di-jet mass: m = m*sqrt( f(pT1) * f(pT2) ) • Rely on massless of jet • Reasonably good? Vanya BELYAEV

  32. Di-jet mass resolution M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=1 ps m(v-p0)=120 GeV/c2,t(v-p0)=0.1 ps, t(v-p+)=10 ps m(jj) [GeV/c] M(H)=180 GeV/c2, m(v-p)=70 GeV/c2 , t(v-p)=1 ps m(jj) [GeV/c] m(jj) [GeV/c] Vanya BELYAEV

  33. 4jet mass resolution: no corrections M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=1 ps [GeV/c2] m(jjjj) Vanya BELYAEV

  34. 4-jet mass resolution: no corrrection M(H)=180 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=100 ps [GeV/c] m(jjjj) Vanya BELYAEV

  35. Nice but a bit misleading plot Efficiency to find a reconstructed jet slope? ~20% bias possible plateau? [mm] vp flight path Vanya BELYAEV

  36. Next steps: Background • Lets concentrate on H→4b • There exist some ground to suspect 4b production as major background • Studied by Can Kilic, Matt McEvoy and David Kaplan from John Hopkins University • Matt has kindly produced Pythia partonic events in LHCb acceptance using ALPGEN generator • 98 events in relatively old format • Use the first two events as input for Gauss • Tested! It works! • A lot of adaptation work ( ALPGEN→ PYTHIA ) • Bunch of new code for Gauss • Need to find a good way to continue and extend the collaboration! • Need to consider also other background sources, e.g. 2b2j Vanya BELYAEV

  37. Next steps: Background • We are almost ready to put the request for the production of background events • Central LHCb production probably is impossible due to the usage of the external input generator files. • I am going to use Syracuse Linux cluster • Start in one or two weeks • Hope to get O(20k)/week • Providing the availability of generator files.. • However if more background events are needed O(200k), it will require the integration of ALPGEN in Gauss • The only way to use LHCb central production Vanya BELYAEV

  38. Next important steps • Study for b-tagging: • non-pointing tracks • leptons • secondary vertices • Jet energy calibration • Correction for the finite flight-path • Checks for HLT alleys acceptances • … • … • … Vanya BELYAEV

  39. Efficiency of generator level cuts Multy-v-pions production m(v-p0)=120 GeV/c2,t(v-p0)=0.1 ps, t(v-p+)=10 ps m(v-p0)=35 GeV/c2,t(v-p0)=100 ps, t(v-p+)=∞ m(v-p0)=50 GeV/c2,t(v-p0)=10 ps, t(v-p+)=∞ m(v-p0)=70 GeV/c2,t(v-p0)=1 ps, t(v-p+)=∞ Vanya BELYAEV

  40. Efficiency of generator level cuts v-particles through Higgs M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=10 ps M(H)=180 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=100 ps M(H)=180 GeV/c2, m(v-p)=50 GeV/c2 , t(v-p)=10 ps M(H)=180 GeV/c2, m(v-p)=70 GeV/c2 , t(v-p)=1 ps M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=1 ps M(H)=120 GeV/c2, m(v-p)=35 GeV/c2 , t(v-p)=100 ps Vanya BELYAEV

More Related