The Hidden Valley and ATLAS Dan Ventura U.Washington Particle Theory Journal Club 01 June 2007

1 June 2007U. Washington PTJC2

1 June 2007U. Washington PTJC3 Outline Introduction to Hidden Valley models –Specialize to QCD-like Hidden Valley with 2 light flavors Production of Hidden Valley particles –Via the Higgs and the Z´ –Experimental signatures & issues of Hidden Valley type models

1 June 2007U. Washington PTJC4 What is a Hidden Valley SM extended by a non-abelian gauge group G v –SM → SM x G v All SM particles are neutral under G v There are new “light” particles (v-particles) charged under G v and neutral under the SM Interactions between the v-particles and SM are mediated by new heavy communicators (Z´ or loop of heavy particles carrying both SM and G v charges)

1 June 2007U. Washington PTJC5 Conceptual Diagram The heavy communicators that carry both SM and G v charge were rarely produced at LEP and LEPII Energy Inaccessibility

1 June 2007U. Washington PTJC6 Hidden Valley Let G v = U(1)´ x SU(n v ) The U(1)´ is broken by a scalar expectation value  giving a Z´ a mass of ~3 TeV The SU(n v ) confines on a scale of ~100 GeV <  v < 1 TeV

1 June 2007U. Washington PTJC7 QCD-like Hidden Valley Consider a Hidden Valley with 2 light flavors ( U V & C V ) m U ~m C <<  V-QCD Particle spectrum controlled by approximate v-isospin symmetry v-hadrons decay promptly to v-pions & v- nucleons V-nucleons are stable The SM neutral  v ± are stable unless FCNC allows C V →U V

1 June 2007U. Washington PTJC8  v 0 Decays  v 0 has the wave function UU - CC and can decay via Q V Q V → Z´→ f f  v 0 decays predominately to heavy flavor ( b b or  for m  < 2 m t ) Free Parameters

1 June 2007U. Washington PTJC9  v Production via the Higgs The potential for the scalar fields is: –V= -  2 |H| 2 -   |  | 2 +  |H| 4 +  |  | 4 +  |  | 2 |H| 2 After SSB, H and  fields mix –The produced higgs state is: cos  |h> + sin  |  > –Then the SM higgs can decay into the HV through the  ˆ v0 v0 Mixing h hvhv v0 v0 g g

1 June 2007U. Washington PTJC10 Hidden Valley in ATLAS Rome La Sapienza Guido Ciapetti Carlo Dionisi Stefano Giagu Daniele DePedis Marco Resigno Lucia Zanello Barbara Mele* U. Washington Henry Lubatti Giuseppe Salamanna Laura Bodine Dan Ventura Matt Strassler* Rome1 - Seattle Collaboration *Theoretical consultants (not ATLAS members) Rome1-Seattle working group formed in Sept All work presented is property of the ATLAS collaboration and was preformed by members of the Rome1-Seattle WG

1 June 2007U. Washington PTJC11 Parameters Parameters used in the current study: –m h = 140 GeV m Z´ = 3 TeV –m  = 40 GeV 250 mm -- for  v from higgs decays 100 mm -- for  v from Z´ decays Lifetimes were chosen to give a distribution of decay positions throughout the inner detector { c   =

1 June 2007U. Washington PTJC12 Event Signatures Pixel Layers Silicon Layers TRT Radial Position of “truth” vertices For gluon fusion: Highly displaced vertices O (10 cm - 1m) –Jets with few tracks SM Backgrounds: Interaction of neutrals with detector material

1 June 2007U. Washington PTJC13 Jets from HV decays gg→h→  v  v Number of reconstructed jets per event Number of reconstructed tracks per jet nTracks Jet cut: E T > 35 GeV Final state has 4 b quarks -- not 4 b jets Number of jets depends on the boost and decay position of  v

1 June 2007U. Washington PTJC14 gg→h→  v  v Pixel detector Silicon tracker TRT mm mm mm  White tracks are MC “truth” tracks  Green tracks are reconstructed  v decay ~ 50 cm from the interaction point (IP)  v decay ~ 5 cm from IP with associated tracks

1 June 2007U. Washington PTJC15 Jet 2 nd  v does not produce a jet -- the decay products are not energetic enough and are too spread out to form a jet

1 June 2007U. Washington PTJC16 Muons from HV decays Muons are produced from the semi- leptonic decays of B-mesons (or  decays) Produced at large distances from the IP Backgrounds: SM  ± and K decays in flight

1 June 2007U. Washington PTJC17 Muons from displaced vertices Longitudinal Impact Parameter Reconstructed Muon track  v decay vertex

1 June 2007U. Washington PTJC18 Muon Impact Parameters Reconstructed longitudinal impact parameter -- Distance from the IP Reconstructed radial impact parameter 1.5 m

1 June 2007U. Washington PTJC19 Triggering on muons from HV decays 7.5 m 2.5 m Level 1 triggers

1 June 2007U. Washington PTJC20 Triggering on muons from HV decays Level 2 triggers Full granularity of data is available within region of interest (RoI) around the “infinite momentum path” as defined by level 1 Refined P T measurement preformed Outside-in tracking is preformed to match the muon spectrometer track to an inner detector track If P T < threshold or if no matching track is found, the trigger fails

1 June 2007U. Washington PTJC21 Muon Trigger results ≥ 6 GeV ~17% of events ≥ 10 GeV ~13% of events ≥ 20 GeV ~6% of events Level 1 muon triggers Level 2 muon triggers ≥ 2 GeV “loose” trigger ≥ 6 GeV ≥ 20 GeV

1 June 2007U. Washington PTJC22 Other higgs production mechanisms Vector Boson Fusion –Higgs produced with 2 forward jets Higgsstrahlung –Higgs recoils against the W h0h0 W/Z q q q1q1 q2q2 q3q3 q4q4 h0h0

1 June 2007U. Washington PTJC23 Longer lifetimes or boosted  v W decay  v decays inside ID 2 nd  v decays at the end of the HCal Hadronic shower occurs inside the Muon Spectrometer

1 June 2007U. Washington PTJC24 For a particular model. Others may differ by ~ factor of events/year q qQ Q Z’  v production via the Z´  Many v-hadrons are formed.  ± v and v- nucleons are stable -- give MET   0 v decay to bb (  )

1 June 2007U. Washington PTJC25 Z´ decay to  v Pixel detector ~12 cm EM Cal ~1.1 m  v decays inside the HCal -- will cause punch through

1 June 2007U. Washington PTJC26 Trigger Rates Jet triggers: –~75% of events pass Level 1 single jet triggers –~70% pass level 1 multi-jet triggers Muon triggers: –80% of events pass level 1 6 GeV muon trigger –8.2% pass level 2 muon trigger ~10% of these muon triggers are caused by punch through

1 June 2007U. Washington PTJC27 Work in progress … Level 1 triggers are hardware based –Cannot be changed at this point Level 2 triggers are software based –Still being written/implemented Can still be modified -- We are currently looking for a set of level 2 trigger objects that will keep our events without letting in SM backgrounds