Forward Physics at LHC

Transcription

1 1 Forward Physics at LHC Risto Orava University of Helsinki and Helsinki Institute of Physics Physics Objectives & Background A Case Study at LHC - ATLAS Detectors for the Forward Spectrometer Planned Project Activities Summary 4th Nordic LHC Physics Workshop Risto Orava Stockholm November 2001

2 Physics Objectives - Tagged forward proton facility at LHC Search for new physics signals Threshold scan for new massive states in pp p+x+p Extension of the physics reach of present LHC exps into the forward region Luminosity measurement with 5 % QCD: σ tot, elastic scattering, soft & hard diffraction, multi rapidity gap events Possible extension to a full acceptance detector*. * F. Gianotti, M. Pepe Altarelli, hep/ex/ , Felix-proposal, K.Eggert et al. 2

3 Physics Objectives... 3 Gluon factory: 100,000 high purity (q/g = 1/3000) gluon jets with E T > 50 GeV in 1 year; gg-events as Pomeron-Pomeron luminosity monitor Searches for new resonant states Higgs (250 H bb events per year with m H = 120 GeV, L=10 34 )*, glueballs, quarkonia 0 ++ (χ b ), gluinoballs - background free environment (bb, WW & τ+τ decays) Squark & gluino thresholds - thresholds are well separated - practically background free signature: multijets & missing transv. energy - model independence (missing mass!) - expect events for gluino/squark masses of 250 GeV - interesting scenario: gluino as the LSP with mass window GeV (S.Raby et al.) Several events with isolated high mass γγ pairs, extra dimensions *V. Khoze et al.

4 Aims 4 Challenges for the forward detector system: operate close to the beam in intense radiation environment meet the constraints due to limited amount of space available The Helsinki group has developed a basic detector concept that meets these challenges. The design and construction of a complete prototype is in progress, to be validated in a test beam. The project constitutes a realistic & physics motivated continuation of the previous 15 years of experimentation with DELPHI Experience with silicon & gas detector techniques b-tagging & jet reconstruction techniques Event portrait (partonometry) techniques

5 Aims... 5 Forward physics is not covered by the base line designs of the main experiments at LHC (ALICE, ATLAS, CMS or LHCB). Additional physics coverage can be achieved with a modest extension of these experiments beyond their acceptance limit of η =5. Detection and momentum measurement of leading protons tagged forward proton physics at the LHC.

6 Elastic Scattering and Diffraction 6 logσ Coulomb scattering: dσ/dt 1/t 2 p 1 p 1 Coulomb&Strong Inteference: ρ Pomeron exchange exp(bt) Structure pqcd p 2 p t (GeV/c) 2 Region Characteristic t (GeV/c) 2 Run type 1 Coulomb region 10-4 super β* Coulomb Strong Interference 10-3 high β* Pomeron Diffraction 10-3 high/low β* Structure Peaks & Bumps 0.8 low/high β* Large t Perturbative QCD 5 low β* 1 The official LHC optics is based on low β*=0.5m and high β* =1100m.

7 Double Pomeron Exchange 7 The Pomeron has the internal quantum numbers of vacuum. PP: C = +, I=0,... 2π p 1 p 1 P P p p 2 2 P: J P = 0 +, 2 +, 4 +, gg vs. uu, dd, ss, cc, bb? Two types of signatures φ 0 Gap η min Jet+Jet η η max Gap proton:p 2 rapidity gap diffractive system rapidity gap proton:p 1 Rapidity Gap Survival Probability 1 Tevatron LHC CD 5-14% 2-11% η min η max 1 V.A.Khoze,A.D.Martin and M.G.Ryskin, hep-ph/

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9 Overall Detector Layout 9 Q1 Q2 Q2 Q3 D1 D2 Q4 IP available 150 m [0.01-4] GeV m 0.01 GeV 2 same layout at the opposite side of the Interaction Point

10 10 Integration and Services electrical and cryogenics lines microstation #1 microstation #2 microstation #3 microstation #4 microstation #5 electrical cryogenics lines

11 Interface side Electrical connectors - oblongs 11 Emergency trigger Cooling connectors - circular

12 12 Emergency actuator Inch worm motor Inner tube for rf fitting Space for encoder Detector Space for cables and cooling link

13 Research and Development: 13 µstations Beam impedance, electromagnetic pick-up bench measurements, shielding. Alignment, mechanical stability and reliability, emergency detector retraction from the beam. Cooling and cryogenic system studies. Bakeout tests, outgassing and vacuum tests. Study of radiation hardness of the critical components: motors, connectors and feedthroughs, flexible connections at cryogenic temperatures in

14 Acceptance Inventory 14

15 Expected Performance -Observables 15 Charged particles from inelastic events: Pseudorapidities: 5.7 < η < 8.4 with nominal LHC optics Leading protons Elastic protons: -t > GeV 2 incl. 240 m: -t > GeV 2 (Angeles Faus-Golfe) Diffractive protons: ξ > 0.01 or -t > GeV 2 with high β (β = 1100m) LHC optics

16 Double Pomeron Exchange and Higgs 16 M H 2 = ξ 1 ξ 2 s p 1 P P H p 1 In symmetric case (ξ 1 = ξ 2 = ξ) for M H = 140 GeV: ξ = 0.01 (ε = 40%) σ(pp p+h+p) = 2-4 fb at s = 14TeV p 2 p 2 M 3.0 GeV achievable

17 Reconstruction of Colour Dipoles? 17 Consider a pair of jets at large p T in high energy pp collisions: In pqcd this is due to a gluon exchange in parton-parton scattering. In hadronization, colour must be exchanged in order to make colour singlet pre-clusters, i.e. there are colour dipole systems between the proton fragments and the hard scattering final states. In diffractive scattering a colour singlet Pomeron is exchanged, and colour dipoles are formed locally, between the closest jets and proton fragments, or in DPE, between the created jet-pairs. q q colour dipole colour dipole P P colour dipole Rapidity gaps filled by soft gluon exchange Rapidity gaps between the colour dipole and protons

18 Proposed Project Activities 18 Running-in phase at Tevatron (CDF): invaluable training ground for students hands-on preparation for a contribution to LHC learn about the challenges of forward physics by using real data provide Ph.D. students and young post-docs with an opportunity to gain visibility in the high-energy physics community

19 Proposed Project Activities: LHC The forward physics project: intensive study on physics performance simulations until summer define the optimal layout of the detector locations / geometry assess physics potential (together with phenomenology groups i 19 R&D on the microstation concept to converge engineering prototype to be finished in 2001 design and construction of a fully functional prototype in collaboration with the LHC machine groups validate the microstation concept in a test beam (autumn 2002) design and construction of a production prototype

20 Proposed Project Activities: LHC 20 machine supporting activities luminosity measurement beam diagnostics microstation/roman pot development to be carried out in collaboration with the machine groups selection of the detector concept LHCb Si-detectors RD39 cryogenic Si-detectors join the general forward physics effort at LHC-Totem

21 21 LHC Running Scenarios LHC is likely to be commissioned with small initial beam currents (first superconducting machine designed for large beam currents, control of beam halo particles, collimation ) => 2-3 years of running-in at cm -2 s -1? Perfect for forward physics! Short dedicated runs (1-2 days) at nominal & Tevatron energies with high(1100m) /initial (18m) /intermediate (160m) β*, luminosities of to 3 x cm -2 s -1 (large -t), bunches 36 to 2835 (10 28 cm -2 s -1 = mb -1 day -1 )

22 Summary 22 LHC Forward Physics project offers: Frontline physics contribution to LHC program (Higgs, supersymmetry...) Physics Problem - Simulation - Detector Development - Detector Construction - Physics Analysis Fundamental Discoveries in Physics. Ideal Training Ground for Students & Technical Trainees LHC Forward Physics projects needs: PostDoc & PhD Positions for young & brilliant experimentalists Long term & stable funding for detector R&D, tests, construction & operation General forward physics framework at LHC