Physics at LHC Dino Goulianos Diffractive Physics What

Physics at LHC Dino Goulianos Diffractive Physics: What answers do we expect from the LHC? Mario Deile CERN PH-TOT 02. 10. 2008 Mario Deile – 1

Dominant Event Classes in p-p Collisions ~65 mb Elastic Scattering ~30 mb Single Diffraction ~10 mb ~ 58 % M ~7 mb Double Diffraction Double Pomeron Exchange M ~1 mb ~ 42 % Processes with large cross-sections! << 1 mb Mario Deile – 2

Signatures of Diffractive Events • By rapidity gap: SD DPE X Rapidity Gap (MX 2 = s) p -ln Rapidity Gap X Rapidity Gap -ln 1 (MX 2 = 1 2 s) -ln 2 Reconstruct proton momentum loss = p/p from diffractive system X (inelastic component): or from rapidity gap: needs good rapidity coverage • By leading protons: needs detectors in beam-pipe insertions far from IP close to the beam (e. g. Roman Pots, moving beam pipes etc. ); Already done at ISR, Spp. S, HERA, RHIC, Tevatron. Particularly strong focus on leading proton measurement at LHC. Roman Pots on both sides of the IPs. Mario Deile – 3

LHC Experiments: Pseudorapidity Acceptance HF: calorimeter T 1: CSC tracker CASTOR: calorimeter (initially on 1 side of IP 5) T 2: GEM tracker TOTEM Roman Pots: horizontal and vertical with ‘edgeless’ Si detectors FP 420, IR 3 0 m 6 m 14 m 16 m 140 m 147 -220 m 420 m, ~7 km RP 220 project for diffraction: ALFA (RP 240): vert. RP and movable beampipe vertical Roman Pot with scintillating fibres LUCID: Cerenkov tubes for relative lumi. calib. for absolute lumi. meas. LHCf: tracker and calo forward n, p 0, g LHCf 0 m 17 m FP 420 140 m 220 m 240 m 420 m

ALICE: diffractive gap trigger No Roman Pots, but Zero Degree Calorimeter for neutral particles. Identify diffractive events by their rapidity gap and leading neutrals from N* excitations. See presentation on ALICE diffractive physics programme by R. Schicker. Mario Deile – 5

Total p-p Cross-Section COMPETE: ~ ln 2 s or ~ s 0. 08 or ~ ln s ? Disagreement E 811–CDF: 2. 6 Typical range of model predictions: 90 – 130 mb. Aim of TOTEM / ATLAS at the LHC: ~ 1 – 2 % accuracy [PRL 89 201801 (2002)] “radius increases” Mario Deile – 6

Total Cross-Section and Elastic Scattering at low |t| Optical Theorem: Coulomb scattering Coulomb-Nuclear interference Nuclear scattering a = fine structure constant f = relative Coulomb-nuclear phase G(t) = nucleon el. -mag. form factor = (1 + |t| / 0. 71)-2 r = Re / Im Telastic, nuclear(t = 0) Mario Deile – 7

Total Cross-Section and Elastic Scattering at low |t| Optical Theorem: Coulomb scattering Coulomb-Nuclear interference Nuclear scattering a = fine structure constant f = relative Coulomb-nuclear phase G(t) = nucleon el. -mag. form factor = (1 + |t| / 0. 71)-2 r = Re / Im Telastic, nuclear(t = 0) TOTEM Approach: Measure the exponential slope B in the t-range 0. 002 - 0. 2 Ge. V 2 , extrapolate d /dt to t=0, measure total inelastic and elastic rates (all TOTEM detectors provide L 1 triggers): Mario Deile – 8

Total Cross-Section and Elastic Scattering at low |t| Optical Theorem: Coulomb scattering Coulomb-Nuclear interference Nuclear scattering ATLAS Approach: Measure d /dt down into Coulomb region and use el. -mag. cross-section for normalisation a = fine structure constant f = relative Coulomb-nuclear phase G(t) = nucleon el. -mag. form factor = (1 + |t| / 0. 71)-2 r = Re / Im Telastic, nuclear(t = 0) TOTEM Approach: Measure the exponential slope B in the t-range 0. 002 - 0. 2 Ge. V 2 , extrapolate d /dt to t=0, measure total inelastic and elastic rates (all TOTEM detectors provide L 1 triggers): Mario Deile – 9

Elastic pp Scattering at 14 Te. V: Model Predictions Islam Model: * = 2625 m (ATLAS) * = 1540 m * = 90 m * = 2 m 3 -gluon exchange at large |t|: Big uncertainties at large |t|: Models differ by ~ 3 orders of magnitude! TOTEM will measure the complete range with good statistics Mario Deile – 10

Detection of Diffractively Scattered Protons Transport equations: TOTEM: Proton Acceptance in (t, ): (x*, y*): vertex position ( x*, y*): emission angle = p/p RP 220 = 0. 5 m - 2 m y [mm] Example: Hit distribution @ TOTEM RP 220 with * = 90 m resolved (contour lines at A = 10 %) vertical Si detector 10 horizontal Si detector t ~ -p 2 * 2 Optics properties at RP 220: vertical Si detector x [mm] x(mm) = 1540 m L = 1028 – 2 x 1029 95% of all p seen; all = 90 m L = 1029 – 3 x 1030 65% of all p seen; all = 0. 5 – 2 m L = 1030 – 1034 p with > 0. 02 seen; all t Mario Deile – 11

Diffraction at * = 0. 5 – 2 m with high Luminosity FP 420 Project (IP 1 and IP 5) RP 220 RP 147 FP 420 lg( ) movable beampipe: 3 D Si trackers and timing detectors Protons seen for > 2. 5 % lg (-t [Ge. V 2]) Alternative idea: put detectors in momentum cleaning region IR 3 ( talk by K. Eggert) Mario Deile – 12

Measurement of Diffractive Cross-Sections Aim: measurement of all kinematic variables and their correlations. Single Diffraction: (Regge theory) p M p Pomeron flux in proton ~ eb t / 1+2 e t Pomeron-proton cross-section ~ (s )e p Slope parameter at LHC: b ~ 5 – 7 Ge. V-2 ? distance of diffractive interaction R ~ 0. 5 fm and t dependence experimentally confirmed up to Tevatron, but total SD cross-section lower. Difficulty in Single Diffraction: Mass from proton measurement: ( ) ~ 2 x 10 -3 Regge (principally limited to 10 -4 by beam energy spread!) At 14 Te. V? Mass resolved for M > 450 Ge. V need to calculate M directly from diffractive system [K. Goulianos: Phys. Lett. B 358] Mario Deile – 13

Rapidity Gap vs. Proton Momentum Example: Single Diffraction measured with = 90 m (protons with all detected). Proton momentum resolution: = 90 m: p( ) = 1. 6 x 10 -3 Rapidity gap measurement resolution: ( ) = 0. 8 – 1 Compare the proton momentum loss with the rapidity gap : verify = –ln ln gap edge in T 1, T 2 M gap edge in CMS gap edge proton M (SD) [Ge. V] < 1 x 10 -7 <5 proton seen, not resolved, gap not meas. , detectors empty 1 x 10 -7 – 1. 6 x 10 -3 5 – 450 proton seen, not resolved, gap measured 1. 6 x 10 -3 – 0. 045 450 – 3000 measured, gap measured > 0. 045 > 3000 measured, gap not seen, detectors full ZDC gap edge in T 1, T 2 ZDC proton resolution limited by LHC energy spread via proton ( *=90 m) =– ( )/ = 100% -range Mario Deile – 14

Rapidity Gap Survival in Hard Diffraction Diffractive DIS at HERA Tevatron e’ Q 2 e hard scattering g* p IP t jet IP jet Rap. Gap p’ diffractive structure function • shape of function FD similar • normalisation different (factor 10) gap survival probability hard scattering cross-section difference related to (soft) rescattering effects between spectator partons Mario Deile – 15

Rapidity Gap Survival Probability: 2 gaps vs 1 gap R(SD/ND) R(DPE/SD) Suppression similar for 2 gaps and 1 gap Mario Deile – 16

Central Diffraction (DPE) 5 -dimensional differential cross-section: Any correlations? Mass spectrum: change variables ( 1, 2) (MPP, y. PP): normalised DPE Mass Distribution (acceptance corrected) MPP 2 = 1 2 s ; 14 mb / Ge. V (M) = 20 – 70 Ge. V =90 m: (M) = 20 – 70 Ge. V (M)/M = 2 % 1. 4 nb / Ge. V 50 events / (h • 10 Ge. V) @ 1030 cm-2 s-1 sufficient statistics to measure the inclusive mass spectrum Mario Deile – 17

Central Production High gluon fraction in Pomeron (measured by HERA, Tevatron) Use the LHC as a gluon-gluon collider and look for resonances in d /d. M Special Case: Exclusive production X = gg, jj, c 0, b 0, H, SUSY H, glueballs? seen at the Tevatron • clean signature and redundancy: measure both protons and central system • exchange of colour singlets with vacuum quantum numbers Selection rules for system X: JPC = 0++, (2++, 4++ ) Study the kinematic properties of exclusive production (e. g. t-spectrum and p. T distrib. of X), compare with inclusive production (M = X + ? ) Mario Deile – 18

Exclusive Production: Examples Predictions for the LHC: Events at Lint = 0. 3 pb-1 Lint = 0. 3 fb-1 excl Decay channel c 0 (3. 4 Ge. V) 3 mb [KMRS] g J/y g m+m– p + p – K+ K– 6 x 10– 4 0. 018 140 4500 140000 4. 5 x 106 b 0 (9. 9 Ge. V) 4 nb [KMRS] g U g m+m– 1. 5 x 10 -3 0. 5 500 jj ( 1 - 2 > 1, E > 50 Ge. V) 0. 2 nb 60 60000 gg (E > 5 Ge. V) 600 fb 0. 18 180 System M BR = 90 m L = 1029 – 3 x 1030 = 0. 5 – 2 m L = 1030 – 1034 Mario Deile – 19

Other Central Production Processes Odderon = hypothetical analogon to Pomeron with C = -1 QCD: Pomeron = 2 gluons, Odderon = 3 gluons Pomeron – Photon fusion Pomeron – Odderon fusion systems with C = P = – 1 : e. g. J/Y, Y See Photon/Odderon studies by Alice. Mario Deile – 20

Detection of Central Production Ideal scenario: reconstruct kinematics from protons AND resonance decay products ( redundancy!) g J/y g m+m– p + p – K+ K– g U g m+m– L = < 3 x 1030 too low for b, H But: Only possible for small production rapidities y i. e. symmetric events 1 2 MPP 2 = 1 2 s Mario Deile – 21

Detection of Central Production Ideal scenario: reconstruct kinematics from protons AND resonance decay products ( redundancy!) g J/y g m+m– p + p – K+ K– g U g m+m– But: Only possible for small production rapidities y i. e. symmetric events 1 2 MPP 2 = 1 2 s Mario Deile – 22

Diffractive Higgs Production Various Higgs studies: • SM with m. H = 120 Ge. V: x BR (H bb) = 2 fb , S/B ~ 1 • MSSM Mhmax scenario (m. A = 120 Ge. V, tan = 40) MSSM Events / 1 Ge. V Invariant mass calculated from the two protons Lint = 60 fb-1 t = 10 ps x BR (h bb) = 20 fb • NMSSM scenario (mh = 93 Ge. V, ma = 10 Ge. V) x BR (h aa 4 t) = 4. 8 fb but S/B 10 ! [JHEP 0710: 090, 2007] Difficulty of diffraction at high luminosity: Pile-up of several events per bunch crossing; L = 1 x 1034: 35 events / bunch crossing Combinations faking DPE signature: e. g. (single diffraction) + (non-diffractive inelastic) + (single diffraction) Leading protons and central diffractive system have to be matched: timing measurements in leading proton detectors (10 – 20 ps in FP 420) z(vertex) Mario Deile – 23

Summary: Questions on diffraction addressed by the LHC • Total p-p cross-section measurement on the ~1% level • Differential elastic cross-section measured over 4 orders of magnitude in t with very different scattering mechanisms • Event topologies and differential cross-sections of diffractive processes (Tools: leading proton detectors, different specially designed beam optics, good rapidity coverage) • Rapidity gap studies based on proton tagging • Study of central production with search for resonances: inclusive vs exclusive processes Mario Deile – 24

Mario Deile – 25

Mario Deile – 26

CMS+TOTEM Forward Detectors T 1: 3. 1 < < 4. 7 CSC trackers T 2: 5. 3 < < 6. 5 GEM trackers HF 10. 5 m T 1 T 2 CASTOR ~14 m Roman Pots: calorimeter RP 147 RP 220 ZDC Symmetric experiment: RPs on both sides! Unique tool for diffraction Mario Deile – 27

CMS + TOTEM: Acceptance largest acceptance detector ever built at a hadron collider T 1, T 2 CMS Roman Pots d. Nch/d 90% (65%) of all diffractive protons are detected for * = 1540 (90) m Charged particles *=90 m ZDC CMS d. E/d central CMS Energy flux = - ln tg /2 T 1 HCal RPs T 2 CASTOR *=1540 m Mario Deile – 28

Leading Proton Detection: TOTEM Roman Pots Roman Pot Unit Horizontal Pot Vertical Pot BPM “edgeless” Si strip detectors (10 planes per pot) Leading proton detection at distances down 10 sbeam + d Need “edgeless” detectors (efficient up to physical edge) to minimise width d of dead space. TOTEM: specially designed silicon strip detectors (CTS), efficient within 50 mm from the edge Mario Deile – 29

Leading Proton Detection: FP 420 (IP 1 and IP 5) and ATLAS RP 220 Proton spectrometers proposed: at 220 m and ~420 m from IP 1 and at ~420 m from IP 5 Two (or three) stations for each spectrometer Two pockets for each station: tracking and timing detectors Mechanical design based on movable “Hamburg Pipe”: LVDT Moving Pipe LVDT Gastof Si Box Si Detector STATION Pockets Mobile Plate Fix Plate Mechanical stop 34. 45 mm Maxon Motor Mario Deile – 30

New Idea: Proton Measurement in IP 3 Detects protons from all interaction points. Acceptance in Momentum Loss Mario Deile – 31

ATLAS + LHCf Forward Detectors PMTs ALFA (RP 240): vertical Roman Pot with scintillating fibres for absolute lumi. meas. LUCID: Cerenkov tubes at |z| ~17 m (5. 4< | | <6. 1) for relative lumi. calib. Beam pipe ZDC LHCf: tracker and calo forward n, p 0, g RP 220 project for diffraction: vert. RP and movable beampipe 32

The Experiments: ALFA (IP 1) Roman Pot Unit MAPMTs FE electronics & shield PMT baseplate optical connectors scintillating fibre detectors glued on ceramic supports 10 U/V planes overlap & trigger Roman Pot ATLAS RP RP 240 m Same configuration on the other side of IP 1 ALFA Mario Deile – 33

The Experiments: LHCf (IP 1) TAN Arm 1 140 m Arm 2 scintillating fibers scintillators tungsten layers Silicon layers scintillators tungsten layers Mario Deile – 34

Characteristics of Diffractive Events Non-diffractive events: p Exchange of colour: Initial hadrons acquire colour and break up. Rapidity gaps filled in hadronisation g g Exponential suppression of rapidity gaps: p P(D ) = e- D , = dn/d Diffractive events: p p P P p 1 Exchange of colour singlets with vacuum quantum numbers (“Pomerons”) rapidity gaps with P(D ) = const. 2 p Many cases: leading proton(s) with momentum loss p / p (typically < 0. 1) Mario Deile – 35

Elastic Scattering - from ISR to Tevatron exponential region ds/dt ~ e-B|t| ~ 1. 7 Ge. V 2 ~ 0. 7 Ge. V 2 ~1. 5 Ge. V 2 • exponential slope B at low |t| increases: B ~ R 2 Mario Deile – 36

Elastic Scattering - from ISR to Tevatron Diffractive minimum: analogous to Fraunhofer diffraction: |t|~p 2 2 • exponential slope B at low |t| increases Mario Deile – 37

Elastic Scattering - from ISR to Tevatron ~ 1. 7 Ge. V 2 ~ 0. 7 Ge. V 2 ~1. 5 Ge. V 2 Diffractive minimum: analogous to Fraunhofer diffraction: |t|~p 2 2 • exponential slope B at low |t| increases • minimum moves to lower |t| with increasing s interaction region grows (as also seen from tot) • depth of minimum changes shape of proton profile changes • depth of minimum differs between pp, pˉp different mix of processes Mario Deile – 38

Elastic Scattering Acceptance for elastically scattered protons depends on machine optics ( *) TOTEM: * = 1540 m, 90 m, 2 m ATLAS: * = 2625 m *=1540 m *=90 m 0. 002 Ge. V 2 0. 06 Ge. V 2 *=2 m 4. 0 Ge. V 2 |t| = 6. 5 x 10 -4 Ge. V 2 Coulomb – nuclear cross-over point log(-t / Ge. V 2) 1. 3 mm centre 6 mm Detector distance from beam TOTEM: better extrapolation lever arm with * = 1540 m than with * = 90 m. Expected uncertainty in tot: ~ 1% ~ 5% ATLAS: Expected uncertainty in tot: ~ 2% if Coulomb region can be reached. Measurements down to lowest |t| need reduced beam emittance and very close detector approach to the beam difficult Mario Deile – 39

Measurement of = f(0) / f(0) *=1540 m, e. N=1 mm rad asymptotic behaviour: 1 / ln s for s COMPETE Prediction for LHC: r is interesting for tot: prediction of tot at higher s via dispersion relation: Try to reach the interference region: • move the detectors closer to the beam than 10 + 0. 5 mm • run at lower energy s = 2 p < 14 Te. V: |t|min = p 2 2 Mario Deile – 40

Elastic and Diffractive Fractions of tot el / tot ~ 30% at the LHC ? el/ tot = 50% : black disk limit 0. 3 The proton not only grows but becomes blacker. Saturation? 0. 2 dependence on tot, el 0. 1 SD / total ratio observed to decrease. At 14 Te. V? Various models: Mario Deile – 41

Interpretation of diffractive PDF’s proton PDF’s u, d, s diffractive vs proton PDF’s: • larger gluon content • harder gluon structure Mario Deile – 42

Measurement of Resonances But: Only possible for small production rapidities y i. e. symmetric events 1 2 cc g J/y g m+m– p + p – K+ K– cb Rapidity y Ideal scenario: reconstruct kinematics from protons AND resonance decay products ( redundancy!) 10 -3 1 g U g m+m– L = < 3 x 1030 too low for b, H H (120 Ge. V) 1 10 -3 MPP 2 = 1 2 s Mario Deile – 43

Measurement of Resonances But: Only possible for small production rapidities y i. e. symmetric events 1 2 cc g J/y g m+m– p + p – K+ K– cb Rapidity y Ideal scenario: reconstruct kinematics from protons AND resonance decay products ( redundancy!) 10 -3 1 g U g m+m– H (120 Ge. V) 1 10 -3 MPP 2 = 1 2 s Mario Deile – 44

Higgs (SM, MSSM) SM with m. H = 120 Ge. V: x BR (H bb) = 2 fb 30 fb-1, m = 3 Ge. V: S/B = 11/10 x BR (H WW*) = 0. 4 fb 30 fb-1: S/B = 8/3 MSSM: MSSM Examples: m. A = 130 Ge. V tan = 30 tan = 50 m. A x BR (A bb) 130 Ge. V 0. 07 fb 130 Ge. V 0. 2 fb mh x BR (h bb) 122. 7 Ge. V 5. 6 fb 124. 4 Ge. V 13 fb m. H x BR (H bb) 134. 2 Ge. V 8. 7 fb 133. 5 Ge. V 23 fb tan = 30 tan = 50 m. A x BR (A bb) 100 Ge. V 0. 4 fb 100 Ge. V 1. 1 fb mh x BR (h bb) 98 Ge. V 70 fb 99 Ge. V 200 fb m. H x BR (H bb) 133 Ge. V 8 fb 131 Ge. V 15 fb m. A = 100 Ge. V [from A. Martin] Mario Deile – 45