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Results and Prospects of the TOTEM Experiment

Overview of the TOTEM physics programme and detector at the LHC, as well as the results from LHC-Run I and the upgrade programme. Presented at the SIF 2015 conference in Rome.

dorothyjjohnson
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Results and Prospects of the TOTEM Experiment

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  1. Risultati e Prospettive dell’EsperimentoTOTEM Giuseppe Latino (Firenze University & INFN) (on behalf of the TOTEM Collaboration) SIF 2015 Roma – September 24, 2015 1/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM

  2. Overview • TOTEM physics programme • TOTEM detector @ LHC • LHC-Run I TOTEM physics results • TOTEM upgrade programme • Summary 2/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  3. TOTEM @ CERN Large Hadron Collider (LHC) Proton – Proton Collisions Beam 1 CMS TOTEM Beam 2 IP5 - Total Cross Section- Elastic Scattering - Diffractive Dissociation LHCb IP2 IP8 LHCf MoEDAL ALICE IP1 ATLAS LHC- p-p collisions ats up to 14 TeV- Linst up to ~ 1034 cm-2s-1- started in Fall 2009- 7 experiments 3/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  4. CMS-TOTEM (CMS/TOTEM Physics TDR, CERN/LHCC 2006-039/G-124) - Soft and hard diffraction in SD and DPE (production of jets, bosons, h.f.) - Central exclusive particle production - Low-x physics - Particle and energy flow in the forward region TOTEM Physics Program Overview Stand-Alone - TOTpp with a precision ~ 1-2%, simultaneously measuring (L ind. meth.): Nel down to -t ~10-3 GeV2 and Ninel with losses < 3% - Elastic pp scattering in the range 10-3< |t| ~ (p)2 < 10 GeV2 - Soft diffraction (SD and DPE) - Particle flow in the forward region (cosmic ray MC validation/tuning) 4/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  5. CMS/TOTEM Program LHC, inelastic collisions T1,T2 T1,T2 ~ 60 mb Charged particles Roman Pots Roman Pots dNch/dh Elastic Scattering ~ 25 mb CMS Energy flux ~ 10 mb Single Diffraction M dE/dh TOTEM+CMS CMS ~ 5 mb Double Diffraction Double Pomeron Exchange ~ 1 mb M << 1 mb • @ 7 TeV • (MC) CMS + TOTEM  largest acceptance detector ever built at a hadron collider: the large  coverage and p detection on both sides allow the study of a wide range of physics processes in diffractive interactions 5/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  6. COMPETE Coll. [PRL 89, 201801 (2002)] (~ ln2 s ) Optical Theorem: Three Methods for T Measurement  = 0.140  0.007 (from Compete) 1) Elastic Scattering + Inelastic Scattering + L: no dependence on ρ T 2) Elastic Scattering + L + Optical Th.: no dependence on Ninel Proper tracking acceptance in very forward region required: elastically scattered p detection mandatory 3) Elastic Scattering + Inelastic Scattering + Optical Th.: L -independent 6/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  7. Photon - Pomeron interference  Multigluon (“Pomeron”) exchange e– B |t| Diffractive structure Allowed |t| range depends on beam optics (special high *– lowL runs required for low |t|) and on proton detector approach to the beam Elastic Scattering Cross Section del/dt @ LHC Wide range of predictions; big uncertainties at large |t|.  Importance of measuring whole |t| range with good statistics  t  p22 Angular divergence @ IP: * = (/*) Beam size @ IP: * = (*) Minimal reachable |t|: |tmin| = n2p2/* pQCD |t|–k 7/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  8. Inelastic Telescopes: reconstruction of tracks and interaction vertex; trigger capability with acceptance > 95 % T1:3.1 << 4.7 T2: 5.3 <  < 6.5  T1: 18 - 90 mrad T2: 3 - 10 mrad h = - log(tg(/2)) T1 10.5 m T2 ~14 m Elastic Detectors (Roman Pots):reconstruction of elastically scattered and diff. p Active area up 1-1.5 mm from beam: 5-10 rad RP220 (RP147) ZDC TOTEM Detector Setup @ IP5 of LHC (Same of CMS) Detectors on both sides of IP5 CMS HF HF 8/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  9. TOTEM Detectors RP 147 Package of 10 “edgeless” Si-detectors hit  10 µm Vertical Pot Vertical Pot Horizontal Pots Vertical Pot Vertical Pot T1 (CSCs) hit  1 mm T2 (GEMs) hit  100 µm 9/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  10. beam-optical elements (magnets) ydet scattered proton y* y* beam axis IP5 RP220 220m Proton Transport from IP5 to RP Location Optical functions: L (effective length), v (magnification), D (machine dispersion) - Describe the explicit path of particles through the magnetic elements as a function of the particle parameters at IP - Define t and -range (acceptance) - Depend on LHC machine optics configuration With:  = p/p;t = tx + ty; ti ~ -(pi*)2 (x, y): vertex position at RP location (s) (x*, y*): vertex position at IP (x*,y*): emission angle at IP Proton transport matrix RP IP5 (xmeasured with  5m lever arm spectrometer)  Elastic proton kinematics reconstruction (x*,y*) (for b* = 90 m @ RP220m: Ly = 263 m, vy  0, Lx  0, vx = -1.9 ): Measuredin RP Reconstructed Excellent optics determination ( 0.25% using constraints from proton tracks in RPs, New J. Phys. 16 (2014) 103041) and detector alignment required 10/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  11. Elastic Scattering Cross Section Measurements @ 7 TeV Data taking in various LHC configurations and different RP detector approach to the beam allowed the measurement in a wide range of |t|: 5·10-3 - 3.5 GeV2 11/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  12. del/d|t| Measurement @ 7 TeV: Results A = 506  23.0syst  0.9stat mb/GeV2 A = 504  26.7syst  1.5stat mb/GeV2 B = 19.9  0.27syst  0.03stat GeV-2 |t|dip= 0.53 GeV2 ~ |t|-7.8 None of the theoretical models really fit the data EPL 95 (2011) 41001 EPL 96 (2011) 21002 EPL 101 (2013) 21002 Analysis ongoing on additional data set (2 GeV2 < |t| < 3.5 GeV2) Integrated elastic cross-section: El = El, Meas.+El, Extr. (Lfrom CMS, with 4% unc.) el = 25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured) el = 24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured) 12/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  13. Direct inel Measurement @ 7 TeV: inel =Ninel/L MX > 3.4 GeV/c2 (TOTEM) S. Ostapchenko arXiv:1103.5684v2 [hep-ph] x/sSD dsSD/dx QGSJET-II-4 SIBYLL / PYTHIA8 low mass contribution • Impact of Low-Mass diffraction: • Extrapolation to low MX region: main • source of systematic uncertainty on inel • MinimalMX depends on maximal || • coverage: lower MX reachable  minimal model • dependence on corrections for low mass diffraction • TOTEM (T1+T2: 3.1 < || < 6.5) gives an unique • forward charged particle coverage @ LHC •  direct measurement of inel with lower sys. unc. •  constraint on low mass diffraction cross-section MX > 15.7 GeV/c2 (ALICE, ATLAS, CMS) 13/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  14. T , eland inelMeasurement @ 7 TeV: Summary CMS LHCb Very good agreement: - among TOTEM measurement with different methods (understanding of systematic uncertainties and corrections) -among LHC experiments 14/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  15. del/d|t| Measurement @ 8 TeV * = 90 m data Follow the same analysis steps as @ 7 TeV (optical functions basically the same): Nel and (dNel/dt)|t=0 measurement  T,el andinel with L-indep. method * = 1000 m data Preliminary studies towards  measurement Possibility of  measurement 15/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  16. TMeasurement @ 8 TeV T from L –independent Method el and inelfrom L - and -indepen. el / inel ratio (el / inel = Nel / Ninel) new data available at s = 2.76 TeV PRL 111 (2013) 012001 16/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  17. del/d|t| Measurement @ 8 TeV with High Statistics Nucl. Phys. B899, 527 (2015) Nb = 1: B = b1 (Reference) Nb = 2: B = b1 + b2t Nb = 3: B = b1 + b2t + b3t2 • High statistic data sample allowed a precise del/d|t| measurement (for 0.027 < |t| < 0.2 GeV2) • “Purely” exponential slope excluded with a significance > 7 ( del/d|t| = Ae-B(t)|t|) • Quadratic and cubic polynomials in the exponent well describe data • Using the new parametrisations for extrapolation to t = 0 and applying the optical • theorem, new results for T are found in agreement with previous measurement: • Nb = 1 (previous, purely exponential)  T = 101.7  2.9 mb (with L-indep. method) • Nb = 2 (quadratic polynomial)  T = 100.8  2.1 mb • Nb = 3 (cubic polynomial)  T = 101.2  2.1 mb 17/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  18. Elastic Scattering at Low |t|:  Measurement Optical Theorem: Total (Coulomb & nuclear) Coulomb scattering dominant Coulomb-Nuclear interference Nuclear scattering • a= fine structure constant • = relative Coulomb-nuclear phase G(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71)-2 =  /  [Telastic,nuclear(t = 0)] Measurement of r by studying the Coulomb – Nuclear interference region down to |t| ~ 610-4 GeV2 Reached @ s = 8 TeV, with b* = 1000 m and RP approaching the beam centre @ ~ 3s 18/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  19. Elastic Scattering in the Coulomb-Nuclear Interference Region g g d/dt  |FC+H|2 = Coul. + Had. + Interf.  Constrained by measured e-B(t)|t| TOTEM Preliminary TOTEM Preliminary Preliminary results on direct  measurement @ 8 TeV: Indirect crude  measurement @ 7 TeV (from optical th.):  |r| = 0.145  0.091 Analysis Ongoing 19/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  20. dNch/d in T2 @ 7 TeV TOTEM measurements compared to MC predictions TOTEM measurements “combined” with the other LHC experiments • Previously unexplored forward  range • High “visible” fraction of inelastic cross section:  95% inel - Diffractive events with MDiff > 3.4 GeV/c2 - ND events > 99% • None theoretical model fully describes the data • Cosmic Ray (CR) MCs show a better agreement for the slope: - SYBILL (CR): 4–16% lower - QGSJET-II (CR): 18-30% higher - EPL 98 (2012) 31002 - 20/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  21. dNch/d Measurement @ 8 TeV (I) • Combined analysis CMS (|| < 2.2) + TOTEM (5.3 < || < 6.4) on low-pileup run • of 2012 @ 8 TeV: common trigger (T2, bunch cross.), both experiments read out • Corrected down to PT = 0 MeV/c  direct comparison with MC • Three event samples: “Inclusive” (particles in any T2 arm, > 91% of inel); • “NSD-enh.” (particles in both T2 arms); “SD-enh.” (particles in only one T2 arm) • None MC event generator provides a consistent description of data Inclusive NSD-enhanced SD-enhanced First common paper with CMS: - Eur. Phys. J. C74 (2014) 3053 - 21/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  22. dNch/d Measurement @ 8 TeV (II) Data sample with displaced interaction point parasitical collision at β* = 90 m (2012, 8 TeV)  vertex @ ~11m  shifted  acceptance for T2 Measurement with -unc. uncertainty Total uncertainty Not possible to make reliable measurement in 6.9 <  < 6 due to large amount of material - Eur. Phys. J. C75 (2015) 126 - 22/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  23. Physics Programme for Run II • Stand-alone: repeat same physics programme @ s = 13 TeV • CMS+TOTEM: focus on central diffraction (CD) processes CD (aka DPE)  -double arm proton detection: full reconstruction of initial state kinematics -hermetic coverage for || < 6.5: initial vrs. final state comparison -several physics processes of interest in hard and soft diffraction - potentialities for the search for new physics Preliminary investigation of some physics channels in progress with the analysis of data from joint CMS-TOTEM high * run (90m) @ 8 TeV (2012) The study/search for low cross section DPE processes requires running in high luminosity scenarios: capabilities of resolving event pile-up and multiple proton track reconstruction mandatory...... upgrade programme needed 23/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  24. Upgraded Roman Pot System Two TDRs released:  two complementary projects Already installed in LHC tunnel during LS1 Existing RP220 (vertical + horizontal RPs) RP147 relocated to 203-214m (vertical + horizontal RPs) 24/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  25. TOTEM Stand-alone Upgrade Hit map for b* = 90 m CERN-LHCC-2014-020, TOTEM-TDR-002 (2014) • High * (90 m), special runs, low L • -Scientific objectives of DPE processes studies: • exclusive central diffraction; • low mass resonances and glueball states; • exclusive charmonium state; • search for missing mass and momentum candidates; • diffractive central jet production. • -CMS/TOTEM common data taking • -Lint  1 – 100 pb-1 • -Only vertical RPs, with one (220-N) equipped with • diamond timing detectors (installed in 2015/16) •  TOF measurement on p (resolution of  50 ps) • gives information on Zv • -RPs at 214 m rotated by 8o multi-track • capability (3D pixel Si detector under study for next upgrade) • -Possibility to reach moderate Lwith pile-up up to   1 25/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  26. CMS-TOTEM Upgrade (CT-PPS) CERN-LHCC-2014-021, CMS-TDR-013, TOTEM-TDR-003 (2014) CT-PPS: CMS-TOTEM PrecisionProtonSpectrometer • Low * (0.5 m), standard runs, high L • - Scientific objectives of DPE processed studies: • EWK: LHC as a - collider • - measure   W+W-, e+e-,m+m-, t+t-; • - search for AQGC with high sensitivity; • - search for SM forbidden ZZgg, ggggcouplings… • QCD: LHC as a g-g collider • - exclusive 2 and 3-jets events, with M up to ~ 7-800 GeV; • - inclusive 2 and 4-jets for g(x,Q2) and structure in pomeron; • - test of pQCD mechanisms of exclusive production; • - almost pure gluon jet samples… • BSM: search for new resonances and missing M • - clean events (no underlying pp event); • - JPC quantum numbers 0++, 2++ • -CMS/TOTEM common data taking, Lint up to 100 fb-1 • - CMS-TOTEM common R&D: detectors to be installed • in the relocated (tracking: 3D Si pixel det.) and newly • constructed (timing: quartz Cherenkov det.) horizontal RPs Hit map for b* = 0.55 m (low b* = standard at LHC) 26/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  27. Summary & Outlook • TOTEM detectors fully commissioned and operative during LHC RunI • The analysis of collision data taken in special runs with different beam conditions (* = 3.5, 90, 1000 m, s = 7, 8 TeV) gave the measurements of: - elastic scattering in a wide |t| range (6·10-4 < |t| < 3.5 GeV2) - elastic, inelastic and total p-p cross-section -evidence for non-exponential slope - forward charged particle multiplicity (also in combination with CMS) - forward DD and (ongoing) study of SD and DPE processes • Data taking with * = 1 km (s = 8 TeV): preliminary  measurement • First joint TOTEM/CMS data taking (2012-13, s = 8TeV) with common triggers and both experiments read out: analyses ongoing • LS-1 (2013-14): “consolidation” activities on detectors (electronics upgrade for DAQ and trigger integration with CMS, relocation of RP147) • After LS-1: repeat measurements at higher s; • RP upgrade with timing detectors: CERN-LHCC-2014-020 (TOTEM-TDR-002); diffraction together with CMS (common upgrade of forward proton detectors: CERN-LHCC-2014-021 (TOTEM-TDR-003 ; CMS-TDR-13) • Looking forward for new data taking during LHC Run II !!! 16 27/27 G. Latino – Risultati e Prospettive dell’Esperimento TOTEM SIF 2015 – 24/09/15

  28. Backup Slides

  29. Elastic Scattering: from ISR to Tevatron ISR ~1.4 GeV2 Diffractive minimum analogous to Fraunhofer diffraction: • minimum moves to lower |t| with increasing s •  interaction region grows (as also seen from sT) • depth of minimum changes  shape of proton profile changes • depth of minimum differs between pp, pbarp different mix of processes B1

  30. Beampipes Horizontal Pot Vertical Pot BPM Roman Pots (I) Units installed into the beam vacuum chamber allowing to put proton detectors as close as possible to the beam Protons at few rad angles detected down to  5 + dfrom beam (beam ~ 80m at RP)  ‘Edgeless’ detectors to minimize d Each RP station has 2 units, 5m apart. Each unit has 3 insertions (‘pots’): 2 vertical and 1 horizontal Horizontal Pot: extend acceptance; overlap for relative alignment using common track Absolute (w.r.t. beam) alignment from beam position monitor (BPM) B2

  31. 200m thick Integration of traditional Voltage Terminating Structure with the Current Terminating Structure beam Readout chip VFAT Roman Pots (II) Each Pot: • 10 planes of Si detectors • 512 strips at 45o orthogonal • Pitch: 66 m • Total ~ 5.1K channels • Digital readout (VFAT): trigger/tracking • Hit Resolution: ~ 10 m Detectors expected to work up to Lint ~ 1 fb-1 (no loss of performance during Run I) Edgeless Si detector: 50 μm of dead area B3

  32. I1 I2 current terminating ring biasing ring Al - + SiO2 p+ p+ n-type bulk Integration of traditional Voltage Terminating Structure with the Current Terminating Structure cut edge Al n+ 50µm Si CTS Edgeless Detectors for Roman Pots Planar technology with CTS (Current Terminating Structure) bias gard/clean-up ring (CR) AC coupled microstrips made in planar technology with novel guard-ring design and biasing scheme 50 μm of dead area 50 µm B4

  33. LHC Optics and TOTEM Running Scenarios Acceptance for diffractive protons: t  -p2 * 2: four-momentum transfer squared;  = p/p: fractional momentum loss b* = 90 m b* = 1000 m b* = 0.55 m > 1033 cm-2 s-1 ~1027 cm-2 s-1 Diffraction: > ~0.01low cross-section processes(hard diffraction) Elastic scattering: large |t| Diffraction:all  if |t| > ~10-2 GeV2 Elastic scattering: low to mid |t| Total Cross-Section Elastic scattering: very low |t|Coulomb-Nuclear Interference Total Cross-Section B5

  34. Elastic pp Scattering: Hit Map in RPs Coincidences of tracks reconstructed in left(45) and right(56) sectors: two “diagonals” analyzed independently β* = 3.5m (7σ) β* = 90m (10σ) β* = 90m (5σ) ty Sector 56 Sector 56 x Sector 45 Sector 56 Aperture limitation, tmax Beam halo Sector 45 x[mm] x[mm] x[mm] 7 x1010 protons per bunchInelastic pile-up ~ 0.8 ev. / bx 6 x1010 protons per bunch Inelastic pile-up ~ 0.03 ev. / bx 1.5 x1010 protons per bunchInelastic pile-up ~ 0.005 ev. / bx Hits associated to elastic scattering candidates B6

  35. Optical Functions: Example at * = 90 m L = (*)1/2 sin((s)) v = (/*)1/2 cos((s)) hit distribution (elastic) x = Lxx* + vxx* +D y = Lyy* + vyy *  Idea: Lylarge Lx=0 vy= 0 y(220) = /2x(220) =  (parallel-to-point focussing on y) (m)‏ Optical functions: - L (effective length) - v (magnification) defined by  (betatron function) and  (phase advance); - D (machine dispersion)  describe the explicit path of particles through the magnetic elements as a function of the particle parameters at IP  = p/p (x*, y*): vertex position at IP (x*,y*): emission angle at IP t = tx + ty ti ~ -(pi*)2 B7 G. Latino – TOTEM Physics Summary

  36. * and  Resolution (* = 90 m) Diffractive p Elastic p CERN-PH-EP-2013-173 B8

  37. Roman Pot Alignment wrt Beam Centre: BLM Collimator cuts a sharp beam edge symmetrically to the centre RP approaches this edge until it scrapes … … producing spike in BLM downstream The second RP approaches When both top and bottom pots “feel” the edge: they are at the same number of sigmas from the beam centre as the collimator and the beam centre is exactly in the middle between top and bottom pot B9

  38. TOTEM Roman Pot Alignment Procedures • Pot position wrt LHC beam center: • alignment wrt collimators by approaching the beam “cut edge” (~ 20 mm) • Internal alignment of components within detector assembly: • metrology, local tracks (few mm) • Relative alignment of the pots in a station: • tracks in overlapping regions (Millepede algorithm, few mm) • Global alignment: • track based exploiting symmetries (co-linearity) • of hit profiles for elastically scattered protons, • also allows “left-right” constraints • (< 10mm in x,  20 mm in y) Criticalprocedures (fill-based): movable devices, beam optics variations Top Pot Flip and shift Bottom Pot Finalprecisionachieved: ~ 10(50) mm in x(y)  t/t ~ 0.3-0.6% B10

  39. TOTEM Elastic pp Scattering: Analysis (I) Proton selection cuts - collinearity cuts (left-right): Θ*x,45 Θ*x,56 Θ*y,45 Θ*y,56 (width in agreement with beam divergence) - low ξ cuts: |x*| < 0.6 mm and 2s cut in Dqy* - vertex cuts (beam halo): |x*45 - x*56| < 27 µm - optics related cuts Collinearity in qx* Collinearity in qy* Missing acceptance inQy* Background subtraction - interpolating the background tails (> 3 ) into the signal region (< 3 ) Acceptance correction - assuming azimuthal symmetry -correcting for smearing around limitation edges B11

  40. TOTEM Elastic pp Scattering: Analysis (II) Unfolding of resolution effects: MC based iterative procedure divergence uncertainty β*=3.5m Extrapolation limit unfolding correction β*=90m σ(Θ*)=1.7µrad Normalization (reconstruction efficiencies): Trigger Efficiency (from zero-bias data stream) > 99.8% (68% CL) DAQ Efficiency 98.142  0.001 % Reconstruction Efficiency – intrinsic detector inefficiency: 1.5 – 3 % / pot – elastic proton lost due to interaction: 1.5% / pot – event lost due to overlap with beam halo (depends on RP position wrt beam and diagonals): 4 – 8% (β*=90m); 30% (β*=3.5m) Luminosity from CMS: systematic error of 4% Systematic uncertainties: dominated by L and by analysis t-dependent effects (misalignments, optics imperfections, energy offset, acceptance correction and un-smearing correction) B12

  41. del/d|t| Measurement @ 7 TeV A = 506  23.0syst  0.9stat mb/GeV2 A = 504  26.7syst  1.5stat mb/GeV2 B = 19.9  0.27syst  0.03stat GeV-2 |t|dip= 0.53 GeV2 ~ |t|-7.8 • Analysis steps: • Alignment procedures/corr. • LHC optics calibration • Elastic candidate event sel. • Background subtraction • Acceptance correction • Unfolding of resolution effects • Normalization (recon. eff.) • Luminosity determination System. uncertainties: dominated by L and by analysis t-dependent effects (energy offset, acceptance correction, misalignments, optics imperfections and un-smearing correction) Integrated elastic cross-section: El = El, Meas.+El, Extr. (Lfrom CMS, with 4% unc.) el = 25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured) el = 24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured) B13

  42. Elastic Scattering at low |t|: SystematicErrors Individual contributions to errors: analysis t-dependent: – misalignments – optics imperfections – energy offset – acceptance correction – unsmearing correction analysis normalization: – event tagging – background subtraction – detector efficiency – reconstruction efficiency – trigger efficiency – “pile-up” correction Luminosity from CMS ( 4%) Constant slope for 0.005 < |t| < 0.2 GeV2 Mario Deile – B14

  43. Comparison to some models None of the models really fit Better statistics at large |t| needed (in progress) B15

  44. Dependence of Nuclear Slope B on Energy B16

  45. Inelastic Cross Section Measurement @ 7 TeV All LHC experiments performed direct measurement: inel=Ninel/L • General analysis steps for the measurement • Corrections to the “visible” inel in the given kinematic acceptance region • trigger and event reconstruction efficiency,background rejection and pile-up • (experimental uncertainty dominated by uncertainty on L) • Corrections for “missing” inel • events lost due to (eventually) limited acceptance in central region, • events lost due limited acceptance in forward region, related to • low mass diffraction leading contribution (and uncertainty) B17

  46. Inelastic Cross Section @ 7 TeV: TOTEM Direct T1 and T2 measurement: inel=Ninel/L(Lfrom CMS) tracks Data sample - Oct. 2011 run with β* = 90 m: same data subsets used for the L-independent total cross section measurement - T2 triggered events - Low pile-up: (μ = 0.03) T2 T2 η η η Inelastic events in T2: classification - Tracks in both hemispheres:mainly non-Diffractive minimum bias (ND) and Double Diffraction (DD) - Tracks in a single hemisphere: mainly single diffraction (SD) withMX > 3.4 GeV/c2  Optimized study of trigger efficiency and beam gas background corrections B18

  47. inel@ 7 TeV: TOTEM (Corrections) • Corrections to the “T2 visible” events ( 95%) • - Trigger Efficiency (from zero bias data, vs track multiplicity): 2.3  0.7 % • - Track reconstruction efficiency (based on MC tuned with data): 1.0  0.5 % • -Beam-gas background (from non colliding bunch data): 0.6  0.4 % • - Pile-up (μ= 0.03) (from zero bias data): 1.5  0.4 % • Corrections for “missing” inelastic cross-section • - Events visible in T1 but not in T2 (from zero bias data): 1.6  0.4 % • - Rapidity gap in T2(from T1 gap probability transferred to T2): 0.35  0.15 % • - Central Diffraction: T1 & T2 empty (based on MC): 0.0  0.35 % • - Low Mass Diffraction(based on QGSJET-II-03 MC): 4.2 %  2.1 % • (constrained by elastic scattering measurement, see later) Uncertainty related to L (CMS): 4% Compatible with other similar meas. @ LHC σinelastic = 73.7 ± 0.1stat± 1.7syst± 3.0lumimb - EPL 101 (2013) 21003 - B19

  48. Low-Mass Diffraction: T1+T2 Acceptance QGSJET-II-03: dN/dMdiff MX > 3.4 GeV/c2 (T2 acceptance) T1+T2 (3.1 < || < 6.5) give an unique forward charged particle coverage @ LHC  lower Mdiff reachable: minimal model dependence on required corrections for low mass diffraction Several models studied: correction for low mass single diffractive cross-sectionbased on QGSJET-II-03 (well describing low mass diffraction at lower energies), imposing observed 2hemisphere/1hemisphere event ratio and the effect of “secondaries” sMx < 3.4 GeV = 3.1 ± 1.5 mb B20

  49. Low-Mass Diffraction: Constraint from Nel • Constraint on low mass diffraction cross-section from TOTEM data: • Use total cross-section determined from • elastic observables (via the Optical Theorem) •  no assumption on low mass diffraction • sinel = stot – sel = 73.2  1.3 mb • and the measured “visible” inelastic cross-section for |h| < 6.5 (T1, T2) • sinel, |h| < 6.5 = 70.5  2.9 mb to obtain the low-mass diffractive cross-section (|h| > 6.5 or MX < 3.4 GeV/c2) • sinel, |h| > 6.5 = sinel - sinel, |h| < 6.5 = 2.6  2.2 mb (or < 6.3 mb @ 95% CL) [MC: 3.1  1.5 mb] - EPL 101 (2013) 21003 - B21

  50. Elastic Scattering in the Coulomb-Nuclear Interference Region Experimental data Physics parameters (, …) Theoretical/phenomenological models Comparison • Modulus constrained by measurement: ds/dt  Ae-B(t) |t|B(t) = b0 + b1 t + … • Phase argFH (interference term): very little guidance by data (QED) • Simplified West-Yennie formula: • constant slope B(t) = b0 • constant hadronic phase arg(FH) = p0 (“costant phase”) • Y(t) acts as real interference phase: • General Kundrát-Lokajíček formula: • any slope B(t) • any hadronic phase: • if argFH(t)  “peripheral phase” • if argFH  cost  “central phase” • complex Y(t): B22

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