1 / 13

Diffractive physics at LHC with rapidity gap trigger

Diffractive physics at LHC with rapidity gap trigger . LHCrap-gapNET: initiative to pursue diffractive physics at LHC with rapidity gap trigger Experimental issue: diffractive gap trigger in ALICE

amber
Télécharger la présentation

Diffractive physics at LHC with rapidity gap trigger

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. Diffractive physics at LHC with rapidity gap trigger • LHCrap-gapNET: initiative to pursue diffractive physics at LHC with rapidity gap trigger • Experimental issue: diffractive gap trigger in ALICE • Physics interest: six contributions discussing possible diffractive physics program in ALICE

  2. Diffractive physics at LHC • Surprise in HERA data: ~10 % of events show regions in rapidity without tracks gdiffractive events ( g color singlet gluon exchange) • Diffractive events characterized by leading proton and rapidity gap (g trigger on proton tagging, g trigger on rapidity gap) • Analysis of H1 data show that data from the two methods agree in detail (Frank-Peter Schilling, HERA-LHC workshop, june 2006, CERN) g high interest for rapidity gap trigger at LHC • CMS, ATLAS: L=1034cm-2s-1g 25 overlapping events/bunch crossing • CMS/TOTEM combined data taking is planned • ALICE: L=5x1030cm-2s-1g one event/80 bunch crossings

  3. Acceptance LHC experiments • CMS/TOTEM LOI LHCC 2006-039 • ATLAS 0o calorimeter ZDC • ALICE 0o calorimeter ZDC

  4. ALICE diffractive gap trigger gadditional forward detectors (no particle identification) 1 < h < 5 -4 < h < -1 g definition of gaps h+ , h_ Luminosity L = 5x1030cm-2s-1 : g one interaction/ 80 bunches diffractive L0 trigger (hardware): gap h+: 3 < h < 5 g Dh~ 0.5 gap h-: -2 < h < -4 g Dh~ 0.5 high level trigger (software): -3.7 < h < 5

  5. Rapidity gap trigger in ALICE • two diffractive L0 trigger signals proposed to physics coordinator for day one data taking in ALICE: • TRDsgap AND PixelOR: diffractive trigger single gap • TRDdgap AND PixelOR: diffractive trigger double gap • TRDsgap, TRDdgap are generated in TRD pretrigger system g TOF multiplicity > 2, absence of signal in VOA,VOC • PixelOR asserts the multiplicity > 2 in central barrel

  6. Diffractive production of vector mesons in pp, pA and AA collisions at LHC • L.Szymanowski, L.Motyka • pp gppV, pAgpAV, AAg AAV • Exclusive diffractive heavy vector meson production is sensititive to square of gluon density xg(x,M2V) of target in small-x region gstudy nuclear shadowing and gluon saturation • cross section for pp g pp J/Psi: ds/dy ~ 12 nb (at y=0) g photon-pomeron, odderon-pomeron contributions ( g look for odderon) • Diffractive production of heavy vector meson pairs • one J/Psi by electron decay in central barrel • one J/Psi by muon decay in muon arm needs further studies

  7. Diffractive and electromagnetic processes with rapity gap trigger at LHC • A.Szczurek, W.Schäfer • Measurement of J/Psi photoproduction needs cc measurement due to BR(cc gg J/Psi) • Hadronic decays: cc gp+p- (0.7 %), cc gK+K- (0.5 %) • Work in progress on differential distributions which depend strongly on unintegrated gluon distributions • Double diffractive h‘ production, BR(h‘ gr0g) ~30 %

  8. Time-like DVCS at LHC • D.Müller, K.Kumericki,. K.Passek-Kumericki • Deeply virtual compton scattering (DVCS) reveals information on generalized parton distributions (GPDs) in nucleon and nuclei • GPDs carry information on transverse parton distributions • Time-like DVCS in hadron-hadron collisions: pp g ppg*g ppl+l- DVCS amplitude Bethe-Heitler amplitudes

  9. Ultra-Peripheral collisions at LHC • J.Nystrand • two photon, photo-nuclear reactions • Exclusive vector meson production gA gVA • D.d`Enterria, G.Baur, S.Klein, M.Strikman, J.Nystrand Trento workshop jan. 2007 „Photoproduction at collider energies“

  10. Diffractive Dijet and cc production • A.D.Martin, M.G.Ryskin, V.A.Khoze, A.B.Kaidalov • pp g p + X + p • transverse energy ET of dijet selects events with soft/hard scale g applicability of perturbative QCD • Dijet ET > 10 GeV are dominately gluon jets g study structure of gluon jets, shape and flavour of secondaries as function of ETg perturbative/nonperturbative QCD • Uncertainties in diffractive Higgs production pp g p + H + p • rapidity gap survival factors, Sudakov factors • same uncertainties in dijet, cc production (large cross sections) • Check of uncertainties of diffractive signals of new physics

  11. Multi-pomeron exchange dynamics and gap survival probability • A.D.Martin, M.G.Ryskin, V.A.Khoze, A.B.Kaidalov • Compare double diffractive events with min. bias inelastic events 1) glueball cross section is thought to be large in double pomeron fusion g study and compare resonances in central region 2) Slope α‘ of pomeron trajectory is small α‘ ~ 0.25 GeV-2, t-slope triple pomeron vertex < 1 GeV g mean trans. mom. kt in pomeron wave function large, kt > 1 GeV g mean trans. mom. of secondaries larger than in min. bias events 3) large kt > 1 GeV corresponds to large effective temperature gno suppression of strange quarks g K/π, η/π, η‘/π ratios enhanced

  12. Multi-pomeron exchange dynamics and gap survival probability • A.D.Martin, M.G.Ryskin, V.A.Khoze, A.B.Kaidalov • Study Sudakov factors • Analyze events with full gap on one side, partial gap on the other • Partial gap due to Sudakov effect of QCD radiation • Test of perturbative formalism for exclusive diffraction

  13. Conclusions • Rapidity gap trigger under construction in ALICE • Physics program complementary to CMS/Totem • ALICE unique in r,f,J/Y reconstruction by lepton decays • Rich physics potential

More Related