Forward physics at the LHC: within and beyond the SM(*)

Transcription

1 Forward physics at the LHC: within and beyond the SM(*) São Miguel das Missões, RS, Brazil David d'enterria CERN 1/39 (*) arxiv: [hep ex]

2 Why forward physics? Many interesting (mostly color singlet) scattering process at the LHC are characterized by forward particle production: QCD: elastic, diffractive interactions QCD: low x Higgs: VBF, central exclusive EWK: excl. dileptons, gauge couplings Beyond SM: MSSM Higgs, elastic grav.,... 2/39 h,a,h

3 Forward physics menu 1. Diffractive & elastic collisions: Total cross sections: elastic scatt., single/double diffraction Soft: Gap survival dynamics, p p underlying event,... Hard: dijets, vector bosons, heavy Q, QQbar, Low x QCD: Parton saturation, non linear QCD evolution, multi parton scatt. via: _ (i) forward QQ, jets (p p, p A), (ii) photoproduction (γ p, γ A interactions) 3. UHE Cosmic rays physics: Forward energy & particle flows (p p, p A, A A) Exotica: Centauro events (DCCs?, strangelets?) 4. EWK (two photon, γ W) interacions: Absolute luminosity (~3% QED precision) via: pp γγ p `+` p Triple (quartic) gauge boson couplings via: pp γp pnw (γγ ZZ,WW) 5. Higgs and beyond SM: Vector Boson Fusion Higgs Central exclusive (SM, MSSM) Higgs 3/39

4 Forward capabilities: ATLAS, CMS/TOTEM, ALICE, LHCb 4/39

5 The LHC experiments CMS TOTEM / (FP420) LHCb ALICE ATLAS LHCf / (FP420) 5/39

6 The LHC experiments: (pt,η) acceptance p 14 TeV Particle flow Energy flow Particle production at LHC over ~ 2 ln( s)/mp ~ 20 All phase space virtually covered (1st time in a collider) [plans to instrument also the TAS (6.6< η <8.3) 20 cm slot with quartz fibers] 6/39

7 Forward physics plans at the LHC 1. CMS (Forward EOI submitted Jan.'04, CMS/TOTEM LOI LHCC ): CASTOR, ZDCs, TAS (under consideration), +TOTEM Soft&hard diffraction (w/ TOTEM or rapgaps), low x QCD, cosmic rays, γ p, γ A, γ γ 2. ATLAS (Forward LOI submitted Mar.'04): ALPHA RomanPots (240 m, LOI R&D), LUCID, ZDC (approved 2007) Total p p cross section, soft diffraction, γ A, γ γ 3. ALICE: 4. LHCb: ZDCs, fwd. muon spectrometer Soft diffraction, low x QCD Forward muon spectrometer Low x PDFs 5. TOTEM (approved LHCC July 04): Roman pots (147m, 220 m), trackers (T1, T2) Elastic scattering, total p p cross section, soft diffraction 6. LHCf (approved LHCC 2006): 7. FP420 (R&D collab. LHCC ): EM Calo (ATLAS TAN, 140 m) Cosmic rays (forward γ,π0) 7/39 Feasibility studies for near beam dets. at 420m Exclusive Higgs, new physics,

8 The LHC experiments: zoom at IP5 CMS TOTEM / (FP420) ALICE ATLAS / LHCf / FP420 8/39 LHCb

9 CMS+TOTEM forward detectors TOT EM R Ps 420m TOT EM T2 (FP420) CMS TOTEM / TOT FP420 E ZDC MT 2 TOT EM R CASTOR Ps CASTOR ZDC CMS+TOTEM+FP420: unique experimental setup All phase space virtually covered (1st time in a collider) 9/39 (FP420) 420m

10 CMS+TOTEM forward detectors CMS IP T1/T2, CASTOR ZDC TOTEM T1 (CSC telescope): 3.1 < < 4.7 TOTEM T2 (GEM telescope): 5.3 < < 6.7 Soft diffraction (SD,DPE), MB/UE/MPI CASTOR (W/Q fiber calo): 5.1 < < 6.6 Higgs, MET, diffract., low x QCD, MB/UE/MPI, heavy ions (L1 trigger, centrality,...), CRs ZDC (W/Q fiber calo): > 8.3 (neutral) CRs, heavy ions (L1 trigger, centrality, γ A,...) TOTEM Roman Pots (Si): ±147, ±220 m Leading p: σtot, elastic scatt., diffraction 10/39

11 The LHC experiments: zoom at IP1 CMS TOTEM / (FP420) ALICE ATLAS / LHCf / FP420 11/39 LHCb

12 ATLAS forward detectors LUCID (Cerenkov Tubes): 17 m, 5.4 < < 6.1 Relative luminosity, diffraction (rap gaps) ZDC (W/Q fiber calo): 140m, > 8.3 (neutral) n,γ detection: relative lumi, CRs, heavy ions (L1 trigger, centrality, photoprod,...) ALPHA (Sci Fi in RPs): ±240 m. Abs. lumi (elastic scatt. in Coulomb interf. region) 12/39

13 The LHC experiments: zoom at IP2, IP8 CMS TOTEM / (FP420) ALICE ATLAS / LHCf / FP420 13/39 LHCb

14 ALICE & LHCb forward detectors Forward muon spectrometers: ZDCs also at ±7m,±100m 4.8 < η < < < 4 2 < < 5 Good capabilities for fwd. heavy Q, _ QQ, gauge bosons measurements: (low x PDFs) 14/39

15 Diffractive physics 15/39

16 Pomeron induced processes Diffract./Elastic scatt. (~40% p p σtot): p intact (Roman Pots), rapidity gap(s). Colourless exchange with vacuum quantum numbers: X X X X X X σtot, : Test fundamental QM relations (Froisart bound, optical th., dispersion relat) Soft diffraction (X = anything): Dominated by soft QCD SD, DPE vs. s, t, MX provide valuable info of non perturb. QCD. Contributions to pile up p p events. Hard diffraction (X = jets, W s, Z s...): Calculable (in principle) in pqcd Info on proton structure (dpdfs,gpds), multi parton interactions, discovery physics (DPE Higgs, beyond SM) 16/39

17 Total p p cross section, elastic scattering σtot predictions for LHC vary by +10 %. 20 Luminosity measurement via optical theorem: dn / dt t =0 16 π tot = σ 2 N el N inel 1 ρ exponential region β*=90m L=3x1030 2x109 E710/811 CDF 2.6σ disagreement COMPETE extrapolation for LHC: σtot β* = 2 m 1.5x ± = ± mb TOTEM goal: ~1% precision β* = 90m optics needed (acceptance at low t ) (for β* = 1500m) β* = 90 m * β = 11 m 17/39

18 Low x QCD physics 18/39

19 Parton saturation & evolution at low x Strong rise at low x of gluons (HERA): Radiation controlled by QCD evolution eqs.: Q2 DGLAP: F2(Q2) ~ αsln(q2/q02)n, Q02 ~1 GeV2 x BFKL: F2(x) ~ αsln(1/x)n Linear equations (single parton radiation/splitting) cannot work at low x: Unitarity violated (even for Q2>> 2), collinear & kt factorization invalid Gluon gluon fusion balances parton branchings below saturation scale : Qs2 ~ 1GeV2 (LHC) Enhanced in nuclei (A1/3~6) : Q 2 ~ 5 GeV2 s CGC = effective field theory describes hadrons as classical fields below Qs Non linear JIMWLK/BK evolution eqs. 19/39

20 Low x Low x proton PDF studies 14 TeV : (i) At y=0, x=2pt/ s~10 3 (domain probed at HERA,Tevatron). Go fwd. for x<10 4 (ii) Saturation momentum: Qs2 ~ 1 GeV2 (y=0), 3 GeV2 (y=5) (iii) Very large perturbative cross sections: Prompt γ Drell Yan Jets Heavy flavour W,Z production _ ep, pp? Fwd. production: x2 s/2 x1 s/2 x2min ~ pt/ s e y= xt e y Every 2 units of y, xmin decreases by ~10 20/39

21 Low x Low x nuclear PDF studies 5.5 TeV, 8.8 TeV: (i) Very high s Bjorken x=2pt/ s~30 45 times lower than RHIC! (ii) Saturation momentum (A1/3~6) : Qs2 ~ [5 GeV2]e(0.3y) (iii) Very large perturbative cross sections. Ratio of Pb/p gluon densities:? Armesto, J.Phys.G32:R367 (2006) Nuclear xg(x,q2) unknown for x<10 3! DdE JPG30:S767 (2005) 21/39

22 Case study I: ϒ photoproduction in CMS (Pb Pb) High energy heavy ions produce strong electromagnetic [Dd'E, hep ex/ ] fields due to the coherent action of ZPb = 82 protons: Equivalent flux of photons in EM (aka. Ultra Peripheral, bmin~ 2RA ~20 fm) AA colls.: Max. γ energy: Eγmax ~ 80 GeV (PbPb LHC) γ Pb: max. sγpb 1. TeV sγp(hera) _ QQ diffractive photoprod. (neutron tagging in ZDC) sensitive to xg 2 unexplored xga(x,q2) y=0: x(ϒ) = y~2: x(ϒ)~x(y=0) e y~ /39

23 Case study I: ϒ photoproduction in CMS (Pb Pb) High energy heavy ions produce strong electromagnetic [Dd'E, hep ex/ ] fields due to the coherent action of ZPb = 82 protons: Equivalent flux of photons in EM (aka. Ultra Peripheral, bmin~ 2RA ~20 fm) AA colls.: Max. γ energy: Eγmax ~ 80 GeV (PbPb LHC) γ Pb: max. sγpb 1. TeV sγp(hera) _ QQ diffractive photoprod. (neutron tagging in ZDC) sensitive to xg 2 ϒ e+e tracker+ecal ϒ + tracker+µ chambers ~500 /0.5 nb 1 expected in CMS 23/39

24 _ Case study II: Forward QQ in ALICE (p p) J/ measurement in µ spectrometer (2.5 < < 4): xg(x) at x2~10 5 dσ/dy J/ : NLO CEM w/ varying PDFs 14 TeV [D. Stocco ALICE] QQbar: Sensitive to diff. PDFs and DGLAP vs non linear evolutions log10(x) 24/39

25 Case study III: Forward (di)jets in CMS (p p) [D.d'E hep ex/ ] Forward soft jets (ET ~ GeV): p + p jet1 + jet2 + X (VBF Higgs trigger) Jets in HFs sensitive to : x2 ~ 10 4 Jets in CASTOR (5.1 < η < 6.6): x2 ~ 10 6! Stats. ~107/1 pb 1 (ongoing full jet reco studies) log10(x1,2) Mueller Navelet dijets separated by large y: very sensitive to non DGLAP evolution jet1 y~10 jet2 [A.Sabio Vera] [C.Marquet, Royon] Increased azimuth. decorrelation ~104 dijets (HF±,ET>30 GeV): enough stats. for detailed studies of y evolution 25/39

26 Cosmic rays physics 26/39

27 UHE cosmic rays via extended air showers Cosmic ray energy spectrum: Only indirect measurements (EAS) above Elab ~100 TeV CR energy & mass determined via hadronic MC simulations: Shower development dominated by fwd, soft QCD interactions. Uncertain x106 extrapolations from SppS,Tevatron to GZK limit. LHC: s = 14 TeV Elab = 1017 ev LHCf experiment: n,γ detection 140 m from IP2 Sci fiber/w calo +Silicon strip det. 27/39

28 Calibration & tuning of hadronic models Model predictions of particle multiplicity, energy flow, sigma tot,... differ by large factors: [T.Pierog] [R.Engel] p p 14 TeV ATLAS LHCf ZDCs,LHCf: Measurement of leading baryon (n), neutral meson ( 0,K0s) in pp, pa, AA at Elab~100 PeV: Strong EAS model constraint [CRs collisions: p Air, α Air, Fe Air] 28/39

29 Cosmic rays exotica E~ ev cosmic rays ( Centauro ) events observed: (i) anomalous number of (N~0) electromagnetic secondaries strangelets? (ii) forward long flying (i.e. non interacting) component DCCs? Centauro Normal CMS CASTOR (longitud. segmentation) can access this research programme. 29/39

30 EWK (γ (γ γ,γ γ,γ W,...) physics 30/39

31 Two photon, γ W interactions [U.Dreyer, ECT* UPC Workshop] [K.Piotrzkowski, CMS] Exclusive l+l (e+e,µ+µ ) production γ l + γ l W photoproduction: (e+e in T2/CASTOR) Triple (anomalous?) gauge couplings (µ+µ in muon chambers) (fwd. proton in RPs) QED process: σ known precisely (LPAIR) Signature: back to back leptons RPs: reco of proton ξ w/ resol. of 10 4 ~300 evts./100 pb 1 after CMS µ trigger Absolute p p luminosity within ~3% (theo) Cross calibration of FP420,TOTEM dets. n,p tagging in ZDC/RPs ~50 evts./100 pb 1 in p p 14 TeV [Also quartic couplings via γγ WW,ZZ] 31/39

32 Higgs & beyond SM 32/39

33 Vector Boson Fusion Higgs qq qqh accompanied by forward jets: ~20% of σh 2 jets (pt~20 60 GeV) w/ large η~5 separation Good QCD background rejection : H WW( l±jj ν) H ττ vs. vs. ttbar,ww Z+nj, W+nj, ttbar CMS: Combined HF+CASTOR extends VBF jet tagging efficiency Jet C A S T Jet O R H F H F C A S ~120 GeV RPs@150m RPs@220m T mzdc H O m ~200 GeV H R background jets at central rapidities 33/39

34 Central exclusive exclusive SM Higgs Central exclusive Higgs production: pp p H p Leading proton H decay in central det Leading proton σh = 3 10 fb (SM), x10(0) in MSSM Motivations: Quantum numbers: central system is approx. JPC = 0++ (selection rule) Excellent mass resolution: from protons, indep. of central decay products. Enhanced S/B: Reduced QCD background. H bbar channel accessible CP violation in Higgs sector: directly measurable from protons azimuthal asymm. Discovery channel: in certain regions in MSSM 34/39

35 Central exclusive exclusive SUSY Higgs MSSM h0,h0,a0,h+,h : Tagged proton channel can be the discovery channel in various MSSM scenarios (for similar masses of the 3 neutral Higgs & large tan ) [Heinemann et al. arxiv: ] 35/39

36 Central exclusive Higgs: FP 420 project For mh< 200 GeV, proton tagging acceptance needed at ±420 m FP420 R&D collaboration (ATLAS/CMS under discussion) Novel technologies: (i) Moving beampipe in cold LHC area (ii) Very fast (τ ~10 ps) Cerenkov detectors: GASTOF (gas), Quartic (Quartz) precise leading protons time difference needed: to isolate pp p H p vertex in high luminosity (~20 pp colls.) conditions 36/39

37 many BSM... Transplanckian effects Once you pass the Planck scale s >> MD Large rapidity separation of 2 jets 37/39 Processes with small momentum transfer e.g. : Elastic transplanckian colls.: Study gravity propagation in ED s Signal: dijets with large y, Mjj Giudice, Rattazzi, Wells, NPB 630 (2002)293

38 Summary: forward LHC ATLAS LUCID CMS CASTOR TOTEM T1 TOTEM T2 ATLAS ZDCs CMS ZDCs ATLAS ALFA TOTEM RPs ALICE ZDCs LHCf FP420 38/39

39 Summary: forward LHC p p σtot, elastic scatt. hard diffraction VM photoprod. exclusive Higgs H,h,A, Fdjj dijets gluon saturation, CGC MB/UE/MPI low x PDFs Multiple Parton Interactions Outgoing Parton Proton Outgoing Parton PT(hard) AntiProton Underlying Event Outgoing Parton BFKL UHE cosmic rays Underlying Event Outgoing Parton EWK (γ γ,γ W,...) 39/39

40 Backup slides 40/39