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Inelastic Cross Section and Forward Particles Multiplicity in TOTEM

Inelastic Cross Section and Forward Particles Multiplicity in TOTEM. Giuseppe Latino (University of Siena & Pisa INFN) (on behalf of the TOTEM Collaboration) MPI 2012 CERN – December 3, 2012. 1/20. CMS-TOTEM (largest acceptance detector ever built at a hadron collider)

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Inelastic Cross Section and Forward Particles Multiplicity in TOTEM

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  1. Inelastic Cross Section and Forward Particles Multiplicity in TOTEM Giuseppe Latino (University of Siena & Pisa INFN) (on behalf of the TOTEM Collaboration) MPI 2012 CERN – December 3, 2012 1/20

  2. CMS-TOTEM (largest acceptance detector ever built at a hadron collider) (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) 2/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  3. 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 3/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  4. 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 4/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  5. Inelastic Cross Section @ 7 TeV 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 5/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  6. Inelastic Cross Section @ 7 TeV: 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 CERN-PH-EP-2012-352 6/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  7. 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 7/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  8. Low-Mass Diffraction: Constraint from Nel • Constraint on low mass diffraction cross-section: • 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) • 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] 8/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  9. Inelastic Cross Section @ 7 TeV: Other Meas. sinel = stot – sel (see J. Kašpar talk for σel and σtot measurements) (I) CMS L + Elastic Scattering + Optical Theorem depends on CMS luminosity , elastic efficiencies & ρ: no depenence on low mass diffraction (small L bunches, * = 90 m, |t|min  210-2 GeV2):σinel = 73.5  1.6 mb (large L bunches, * = 90 m, |t|min  510-3 GeV2):σinel = 73.2  1.3 mb (II) (L -independent): Elastic Scattering + Inelastic Scattering + Optical Theorem eliminates dependence on luminosity, depends on  & low mass diffraction models using L- and -independent ratio: σel / σinel = Nel / Ninel = 0.354  0.009 = 0.1410.007 (Compete) EPL 96 (2011) 21002 CERN-PH-EP-2012-239 σinel = 72.9  1.5 mb CERN-PH-EP-2012-353 9/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  10. Inelastic Cross Section @ 7 TeV: Summary (CERN-PH-EP-2012-353) Excellent agreement among measurements: - with different methods (understanding of systematic uncertainties and corrections) -with other LHC experiments 10/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  11. Inelastic Cross Section @ 8 TeV: Results July 2012: runs at b* = 90 m Same analysis strategy as for the measurement @ 7 TeV with the L –independent “method II”: - tot = 101.7  2.9 mb - Nel / Ninel = 0.362  0.011  inel = 74.7  1.7 mb Paper draft approved for submission to journal 11/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  12. Charged Particle Pseudo-Rapidity Density (dNch/d) @ 7 TeV May 2011 run, b* = 3.5 m, low pile-up (  0.03) x T2 alignment • -Internal alignment • two different track-based methods (HIP • and Millepede) implemented in order to • resolve misalignment (x-, y-shifts) among • detectors in a quarter • - Quarter-quarter alignment • using tracks in the overlap region • - Global alignment • each arm aligned (tilts and shifts) respect • to the nominal position by imposing the • symmetry of the “beam pipe shadow” • on each detector plane IP z Finalprecisionachieved: ~ 1 mm (x,y-shifts); ~ 0.4 mrad (plane tilts) 12/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  13. dNch/d in T2: Analysis Highlights Data sample: events at low luminosity and low pile-up, triggered with T2 (5.3 < || < 6.5) Selection: at least one track reconstructed in T2 Primary particle definition: charged particle with  > 0.310-10 s, pT > 40 MeV/c Primary particle selection: -primary/secondary discrimination, data-driven based on reconstructed track parameters (ZImpact) Primary track reconstruction efficiency: -evaluated as a function of the track  and pad multiplicity, MC-based - efficiency of 80% - fraction of primary tracks within the cuts of 75% – 90% ( dependent) Un-folding of () resolution effects: MC driven bin “migration” corrections Systematic uncertainties (< 10%): dominated by primary track efficiency and global alignment correction uncertainty 13/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  14. Secondary Particles in T2 Track reconstruction in T2 is challenging because of the large amount of charged particles generated by the interaction with the material placed between the IP and T2 90% (80% ) of the signal (tracks) in T2 is given by secondaries A detailed revision of the volumes and of the GEANT setting was necessary HF IP HF T2 telescope Effect of the BP on the hit didtribution Material contributing to secondary particle generation: Left: BP flangeand ion-pumps. Right: BP cone at h=5.53 and the lower edge of HF 14/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  15. dNch/d in T2: Primary Track Selection - A fit on the distribution of the track Zimpact parameter is used to separate primary from secondary tracks - We know from MC and data comparison the shape of the primary and secondary track Zimpact distribution (double-gaussian for primaries, exponential for secondaries) - A large part of the secondary contribution can be therefore extracted from the primary region by fitting the track-ZImpact distribution. The fit is repeated for each  bin. Track Z-Impact definition Z-Impact distribution (one quarter, one  bin) T2-track One quarter distribution Double Gaussian Primary Exponential secondary 90° Z0·sign() < 13.5 m 15/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  16. Tracking Performance: PT Acceptance At PT = 40 MeV/c the efficiency, including the Zimpact cut, is  80%. This is also the value which minimizes the inclusion of tracks with PT < 40 MeV/c and the losses on higher PT tracks Multiple scattering and magnetic field effects turn out to determine the primarycharged particle PT acceptance of T2 Particle PT (GeV/c) 16/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  17. dNch/d in T2: Results TOTEM measurements compared to MC predictions TOTEM measurements “combined” with the other LHC experiments 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 High “visible” fraction of inelastic cross section:  95% inel - Diffractive events with MDiff > 3.4 GeV - ND events > 99% Published: EPL 98 (2012) 31002 17/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  18. Joint Data Taking with CMS 2011Ion run: proof of principle • 2012: Ist realization of common running • CMS  TOTEM trigger exchange • Offline data “synchronization” (orbit and • bunch #) + “merging” (n-tuple level) May 2012: low pileup run: b* = 0.6 m, s = 8 TeV, T1 & T2 & CMS read out dNch/dh, correlations, underlying event July 2012: b* = 90 m, s = 8 TeV, RP & T1 & T2 & CMS read out stot, sinel with CMS, soft & semi-hard diffraction, correlations • combined dNch/dh and multiplicity correlations • hard diffraction: p + di-jets (* = 90m) Analyses ongoing: 18/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  19. Ongoing Activity on dNch/d Measurement T2 [T1] • Analyses in progress: • T1 measurement @ 7 TeV (3.1 < || < 4.7) • Combined analysis CMS + TOTEM(0 < || < 6.5) on low-pileup run of May 2012 (@ 8 TeV): common trigger (T2, bunch crossings), both experiments read out • NEW: parasitical collision at β* = 90 m (July 2012, 8 TeV) •  vertex @ ~11m  shifted  acceptance for T2: • - extend  range up to  7.3 (under study) • - cross-check with T1 results in the 3.8-4.8  range (ongoing) 19/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  20. Summary & Outlook • TOTEM detectors fully commissioned and operative • 2011 data taking (s = 7 TeV) in special runs with different beam conditions (* = 3.5, 90 m) allowed the measurementsof: • -inelastic p-p cross-section (with different methods) -dNch/d with T2 (5.3 < || < 6.5) • - analysis ongoing for the dNch/d measurement with T1 (3.1<||<4.7) • 2012 data taking (s = 8TeV) in special runs: • - measurement of inel with L-independent method • - first joint TOTEM/CMS data taking with common triggers and • both experiments read out: analysis ongoing on dNch/d measurement • on the full  range (|| < 6.5) • -special run with displaced vertex @  11m: potentiality of dNch/d • measurement with T2 in the range 3.8 < || < 4.8 (and maybe up to 7.3) • Possibility of dNch/d measurement for different inelastic topologies (ND, SD, DD) under study • Looking forward for more data a higher s 16 20/20 G. Latino – TOTEM Inel. Xsec. and fwd Part. Multip MPI 2012 – Dec. 3, 2012

  21. Backup Slides

  22. TOTEM & CMS @ IP5 of LHC Leading Protons measured at -147m & -220m from IP Castor (CMS) Leading Protons measured at +147m & +220m from IP T2 CMS T1 TOTEM Experiment T1 T2 Castor (CMS) TOTEM Collaboration: Bari, Budapest, Case Western Reserve, CERN, Genova, Helsinki, Penn U., Pisa/Siena, Prague, Tallin (~ 80 physicists) B1

  23. Each arm: • 5 planes with 3 coordinates/plane, each formed by 6 trapezoidal CSC detectors • 3 degrees rotation and overlap between adjacent planes • Trigger with anode wires • Digital readout (VFAT) for ~ 13.5K ch. • Hit Resolution: ~ 1 mm 1/4 of T1 T1 Telescope Ageing studies at CERN GIF: no loss of performance during 12-month test, with ~ 0.07 C/cm accumulated charge on wires, a dose equivalent to ~ 5 years at Linst=1030 cm-2s-1 Fully commissioned and operative B2

  24. Each arm: • 10 planes formed by 20 triple-GEM semi-circular modules, with “back-to-back assembly and overlap between modules • Double readout layer: Strips for radial position (R); Pads forR, f • Trigger from Pads (1560/chamber) • Digital readout (VFAT) for ~ 41.4K ch. • Hit Resolution:R ~ 100 mm,  ~ 1o GEM Technology: • Gas Detector • Rad-hard • High rate • Good spatial and timing resolution strips T2: “GEM” Technology T2 Triple GEM technology adequate to work at least 1 yr at L=1033 cm-2s-1  pads Castor Calorimeter (CMS) Test Beam ~ 0.4 m T2 Telescope Fully commissioned and operative B3

  25. 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) B4

  26. 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 Fully commissioned and operative Edgeless Si detector: 50 μm of dead area B5

  27. LHC, inelastic collisions T1,T2 T1,T2 ~ 60 mb Charged particles Roman Pots Roman Pots dNch/dh Elastic Scattering 18 - 35 mb CMS Energy flux 10 - 16 mb Single Diffraction M dE/dh TOTEM+CMS CMS 4 - 14 mb Double Diffraction Double Pomeron Exchange 0.2 - 1.5 mb M << 1 mb CMS/TOTEM Common Physics Program 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 B6

  28. MX > 3.4 GeV/c2 (T2 acceptance) S. Ostapchenko arXiv:1103.5684v2 [hep-ph] x/sSD dsSD/dx QGSJET-II-4 SIBYLL/PYTHIA8 low mass contribution Low-Mass Diffraction: MC Predictions Mx2 s  ∆  -log Mx2se-∆ 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 B7

  29. 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 Elastic Scattering Differential Cross-Section @ 7 TeV None of the theoretical models really fit the data EPL 95 (2011) 41001 EPL 96 (2011) 21002 CERN-PH-EP-2012-239 Analysis ongoing on additional data set (2 GeV2 < |t| < 3.5 GeV2) Integrated elastic cross-section: El = El, Meas.+El, Extr. (L from CMS) 25.4 ± 1.0lumi ± 0.3syst ± 0.03stat mb (91% directly measured) 24.8 ± 1.0lumi ± 0.7syst ± 0.2stat mb (67% directly measured) B8

  30. Inelastic Cross Section @ 7 TeV: Summary EPL 96 (2011) 21002 CERN-PH-EP-2012-239 CERN-PH-EP-2012-352 CERN-PH-EP-2012-353 B9

  31. Forward Physics: importance of the dN/dh measurement The CR connection: tuning of the MC generator used in the Extensive Air Showers simulations • A good description of the forward particle multiplicity and density produced in p-Air collision is important for the analysis of the Extensive Air Shower produced when a High Energy CR interacts in the athmosphere. • The energy and mass of the primary CR can be understood from measurement on Earth thanks to MCs which simulate the air shower. • 7 TeV pp collisions at LHC correspond to pCR-pAIR collisions with pCR of ~25 PeV. B10

  32. The Beam Pipe “Shadow” on T2 HF IP5 Beam Pipe cone at  ~ 5.54 (>100 radiation lengths) HF B11

  33. T2 Tracking performance: efficiency Event reconstruction efficiency T2 inelastic event detection efficiency (at least a ch. particle generated in the T2 acceptance): 99.5% |ZImpact| < 5m Definition of the track ZImpact parameter: Bin width: 0.05 APM: Average Pad-Cluster Multiplicity Average data APM (7 TeV) B12

  34. Importance of Global Misalignment Track ZImpact before and after the global misalignment correction in data and in a MC, where the misalignment geometry is simulated: Tuned MC Data secondaries primaries Primary/secondary separation is impossible without the global alignment. Maximum tilt angle measured in the data = 8mrad (T2 acceptance: 3-10 mrad !) B13

  35. Tracking Performance:  Resolution Two estimators of h were studied: hIMP and hRZ • IMP= average of the h of the track hits (each one calculated with the vertex at (0,0,0)) • hRZ= pseudorapidity of the track calculated with the polar angle of the track in the RZ plane Resolution: RMS of the difference between the reconstructed h and the generated h. Vtx smearing DZ= 5 cm, 2<E<80 GeVp- Only tracks with |ZImpact|< 5m are included hRZ hRZ hIMP hIMP hIMPimplicitly performs a vertex constraint. Smaller at high hbecause of the smaller contribution of B and Vtx smearing. hRZgrows as Dη ∼ Dθ/θ, more dependent on misalignment. B14

  36. dNch/d in T2: Systematic Errors Evaluation method 1. Data/MC comparison of “half quarter” trk efficiencies Quarter dependent 2. Effect of wrong misalignment parameters on the measured dN/d 3. Maximum variation of the secondaries contamination from different MC. Common to all the quarters 4. Fit/fitting-interval uncertainty 5. MC spectrum and B intensity variation 6. Different MC estimates 7. Data/MC discrepancy on the effect of the cut on the track 2-probability. (*) 8-9. Dedicated analysis on bunch-crossing samples (*) not all the contributions have been added in quadrature B15

  37. Runs Planned for 2012-13 • RP insertions in normal physics runs (b* = 0.6 m)- hard diffraction together with CMS (high diffractive masses reachable) • - proton acceptance:  > 2-3 %, any t - study of closest possible approach of the hor. RPs (i.e. acceptable beam losses) essential for all near-beam detector programmes at high luminosity after LS1 • Collimators needed behind the RP to protect quadrupoles • Request a low-pileup run (m ~ 5 %) with RPs at b* = 0.6 m(in May RPs not aligned) study soft central diffraction final states with 2 leading protons defining Pomeron-Pomeron mass M2 = x1 x2 s (good x resolution at b* = 0.6 m s(M) ~ 5 GeV) • Participation in the p-Pb runs with insertions of the RPs on the proton side study diffractive/electromagnetic and quasi-elastic p-Pb scattering p-Pb test run in September with CMS was successful (T2 trigger given to CMS) B16

  38. pA Minimum Bias Physics [K. Oesterberg, pA @ LHC workshop, June 2012] B17

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