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Giornata del dipartimento di Fisica

Giornata del dipartimento di Fisica. M. Berretti Siena, 21 December 2012. Latest results from the TOTEM experiment. The TOTEM experiment Physics results Ongoing analyses and future. The TOTEM Collaboration.

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Giornata del dipartimento di Fisica

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  1. Giornata del dipartimento di Fisica M. Berretti Siena, 21 December 2012 Latest results from the TOTEM experiment • The TOTEM experiment • Physics results • Ongoing analyses and future

  2. The TOTEM Collaboration • Siena, 21 December 2012 M. Berretti 2

  3. TOTEM Physics Program Overview Stand-Alone: - TOT pp with a precision ~ 1-2% (Lind. meth.) simultaneously measuring : 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) pp elastic, inelastic and total cross section Diffractive processes Forward multiplicities Large rapidity (-ln tan q/2) gap (SD) • Siena, 21 December 2012 M. Berretti 3

  4. The TOTEM experiment at the LHC TOTEM TOTal cross section, Elastic scattering and diffraction dissociation Measurement IP5 CMS The Compact Muon Solenoid ALICE A Large Ion Collider Experiment LHCb The Large Hadron Collider beauty experiment ATLAS A Toroidal LHC ApparatuS LHCf LHC forward experiment • Siena, 21 December 2012 M. Berretti 4

  5. The TOTEM experiment at the LHC TOTEM is composed by 3 different detectors: T1: CSC chambers, charged particle tracking 18<q<90 mrad T2: GEM chambers, charged particle tracking 3<q<10 mrad RP: movable silicon detector: elastic and diffractive proton measurement (optics-dependent acceptance) About 99.5% of all non diffractive minimum bias events and ~85% of all diffractive events have charged particles within the acceptance of the TOTEM detectors (T1 and T2). ALICE A Large Ion Collider Experiment LHCb The Large Hadron Collider beauty experiment ATLAS A Toroidal LHC ApparatuS LHCf LHC forward experiment • Siena, 21 December 2012 M. Berretti 5

  6. One Roman Pot The RP detector Beam Sensitivity up to 50 mm thanks to the Current Terminating Structure 90% Efficiency 10% Efficiency Physical Edge • A RP station: • Composed by 2 units • Each one with 2 Vertical and one Horizontal Pots • Each Pot is equipped with 10 “edgless” silicon planes E.Oliveri • Siena, 21 December 2012 M. Berretti 6

  7. Installation in the CMS endcaps region The T1 detector 3.1 < |η| < 4.7 (h=-ln tan q/2) Cathode Strip Chambers • No loss of performance after a total • charge integrated on the anode wires • of 0.065 C/cm • (5 years at a luminosity of 1030 cm−2s−1) • Hit sX,Y= 1mm T1 individual arm inelastic event reconstruction efficiency : ∼98 % (at least one charged particle in T1 with pT >100 MeV/c) • Siena, 21 December 2012 M. Berretti 7

  8. System set-up, commissioning and software mainly developed from the Siena group The T2 detector 40 Triple Gas Electron Multiplier chambers rmax≈14.45cm 20 Triple GEM (Minus End) rmin≈4.25cm 20 Triple GEM (Plus End) Δϕ=360o IP5 ≈13.8m ≈13.8m qmin≈3mrad ≈0.2o ≈40cm qmax≈10mrad ≈0.6o • Hit sR,f= 0.1mm, 1o T2 inelastic event reconstruction efficiency : ∼99.5 % (at least one charged particle in T2 with pT >40 MeV/c) 5.3≤|h| ≤ 6.5 • Siena, 21 December 2012 M. Berretti 8

  9. The T2 detector 40 Triple Gas Electron Multiplier chambers Drift Installation of 2 T2 quarters GEM foil Transit GEM foil Transit GEM foil Induction Readout Plane Δϕ=192o Δϕ=192o • Advantage of a GEM plane : • High tolerance to radiation (> 50 Mrad) • High rate capability (> 10 MHz/cm2) • Low material budget (10 planes: 0.07 X0) Sensitive Area The large occupancy and the impossibility to resolve the pile-up vertices make T2 usable only for low luminosity runs • Siena, 21 December 2012 M. Berretti 9

  10. TOTEM Physics and results 1. Measurement of the elastic scattering on a wide range of four-momentum transfer. 7 TeV ISR ~ 1.7 GeV2 • Minimum moves to lower |t| with increasing CM energy • Exponential slope grows with the CM energy Large-t region: Important for model discrimination ~ |t|-7.8 ~ 0.7 GeV2 ~1.5 GeV2 • Siena, 21 December 2012 M. Berretti 10

  11. stot= (98.0 ± 2.5) mb Total cross section measurement @ 7 TeV in 3 ways (ρ=0.14[COMPETE]) June 2011 (EPL96): stot = (98.3 ±2.8) mb Oct. 2011 (PH pre.): stot = (98.6 ±2.2) mb different bunch intensities and elastic acceptance ! stot= (99.1 ± 4.3) mb Excellent agreement between cross-section measurements at 7 TeV using - runs with different bunch intensities and RP acceptances. - different methods. • Siena, 21 December 2012 M. Berretti 11

  12. Total cross section measurement @ 7 TeV in 3 ways Luminosity calibration: Estimated by CMS Estimated by TOTEM 1) L= 82/mb ± 4% L= 83.7/mb ± 3.8% 2) L= 1.65/mb± 4% L= 1.65/mb± 4.5 % • Siena, 21 December 2012 M. Berretti 12

  13. TOTEM Physics and results 1. Measurement of the pp total cross section with 1-2% systematic error by using the luminosity independent method • Needs the extrapolation of the elastic rate to t=0 • Needs the total elastic and inelastic rate Obtained in a low luminosity run at b*=90m optics where RP edge approaches at 5s to the beam center. • The visible elastic rate is 90%. The rest is extrapolated with the exponential fit • The inelastic rate is measured triggering with T2. sel =25.1±1.1 mb A = 506 ±22.7syst±1.0statmb/GeV2 B = 19.9±0.26syst±0.04stat GeV-2 Low mass diffraction ~ 3.7% Trigger efficiency ~2.3 % T1 only events ~2% Pile-up (m~0.03) ~ 1.5 % Track reconstruction efficiency ~1% Beam-gas background ~ 0.57% Rapidity Gap in T2 0.5% Central diffraction 0.5% dσEL/dt [mb/GeV2] EPL 96 (2011) 21002 To be published sinel : 72.9 ± 1.5 mb -t [GeV2] • Needs the value of r (From the COMPETE collaboration fit, r= 0.14, later with a direct measurement at b*=1Km ) • Siena, 21 December 2012 M. Berretti 13

  14. NB: Low mass diffraction cross-section can be constrained Estimation of σinel= σtot – σel = 73.2± 1.3mb can be done with RP-only measurement (L-dependent). However, T1+T2 visibleσ<6.5inel= 70.9 ± 2.8 mb σ>6.5inel= 3.7% σ<6.5inel • Needs the total elastic and inelastic rate • The visible elastic rate is 90%. The rest is extrapolated with the exponential fit • The inelastic rate is measured triggering with T2. sel =25.1±1.1 mb sEL =25.1±1.1 mb Low mass diffraction ~ 3.7% Trigger efficiency ~2.3 % T1 only events ~2% Pile-up (m~0.03) ~ 1.5 % Track reconstruction efficiency ~1% Beam-gas background ~ 0.57% Rapidity Gap in T2 0.5% Central diffraction 0.5% sinel : 72.9 ± 1.5 mb sinel T2VIS = 95%sinel • Siena, 21 December 2012 M. Berretti 14

  15. Low mass diffraction: T1+T2 acceptance MX > 3.4 GeV/c2 S. Ostapchenko arXiv:1103.5684v2 [hep-ph] x/sSDdsSD/dx QGSJET-II-4 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 SIBYLL/PYTHIA8 (Mx2 s ) Several models studied: correction for low mass single diffractive cross-section based 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 • Siena, 21 December 2012 M. Berretti 15

  16. Cross section measurements @ 8 TeV July 2012: runs at b* = 90 m  tot = 101.7  2.9 mb  inel = 74.7  1.7 mb Same analysis strategy as for the measurement @ 7 TeV with the luminosity independent method: - Nel / Ninel = 0.362  0.011 • Siena, 21 December 2012 M. Berretti 16

  17. 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. • Siena, 21 December 2012 M. Berretti 17

  18. Forward Physics: importance of the dN/dh measurement • Observation of the extended longitudinal scaling: For very high energy collisions in the reference system with the target at rest, particles produced in the fragmentation regionapproach to a limiting distribution which doesn’t depend anymore on the collision center of mass energy. p-Gold collisions 200 GeV 130 GeV 19.6 GeV • An universally accepted theoretical description is still missing! • The theory of the Color Glass Condensate is a promising approach (TOTEM) Fragmentation region • Siena, 21 December 2012 M. Berretti 18

  19. Measurement of the dNCH /dh in T2 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: sinel95% sinel - Diffractive events with MDiff > 3.4 GeV - ND events > 99% Published: EPL 98 (2012) 31002 • Siena, 21 December 2012 M. Berretti 19

  20. Joint data taking with CMS 2011Ion run: proof of principle • 2012: 1strealization 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, s1/2= 8 TeV, T1 & T2 & CMS read out dN/dh, correlations, underlying event July 2012: b* = 90 m, s1/2= 8 TeV, RP & T1 & T2 & CMS read out stot, sinel with CMS, soft & semi-hard diffraction, correlations • Siena, 21 December 2012 M. Berretti 20

  21. TOTEM analyses in progress Multiplicities • Inelastic dNCH /dh@ 8 TeVCMS + T2 (0 < |h| < 6.5) • Inelastic dNCH /dhT1 measurement @ 7 TeV (3.1 < |h| < 4.7) • Inelastic dNCH /dh@ 8 TeV with the displaced vertex (11m) Main final state topology for inelastic events Diffractive studies • Differential cross section measurement for single diffraction dsSD/dt and double diffraction dsDD/dhmin Single Diffraction Double Diffraction • Double Pomeron exchange cross section (soft and hard), exclusive jet production in CMS in double pomeron exchange Double Pomeron Exchange • Siena, 21 December 2012 M. Berretti 21

  22. TOTEM analyses in progress • Elastic scattering at low-t: studied of the coulomb-nuclear interference, measurement of r • a= fine structure constant • = relative Coulomb-nuclear phase G(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71)-2 Coulomb scattering dominant Total (Coulomb & nuclear) Coulomb-Nuclear interference Nuclear scattering dominant First (preliminary) measurement in the interference region!! • Siena, 21 December 2012 M. Berretti 22

  23. Near future (during LS1): • Extend the multiplicity analyses for each event class (ND,SD, events with Jets in • CMS) . Charged particle correlations. • Data taking p-Pb runs in Jan-Feb 2013 with CMS (s1/2NN=5 TeV). • Multiplicity(T1+T2) and Energy flow (CASTOR & HF) in pp and pPb • After LS1(2014/2015) : • Repeat the stand-alone TOTEM program at the higher LHC energy • Installation/Development of RP-like timing detectors (< 10 ps resolution, Cherenkow light from Quartz + SiPm) + tracking detector (pixels) : this will allow the study of the hard diffraction with CMS (combining the RP protons to the reconstructed CMS vertices) • Siena, 21 December 2012 M. Berretti 23

  24. Conclusions • The TOTEM experiment at LHC is fully operative. • 7 analysis-papers have been published/submitted (on the elastic, • inelastic, total pp cross section @7 and 8 TeV and on the T2 dN/dh • measurement @ 7 TeV) • Fundamental contribution of the Siena University to this • success (installation and commissioning of T2, TOTEM-trigger, • T2 offline and online software...). • Sevaral analyses are ongoing: • Large amount of work done (to do) on analysis of the multiplicties, • correlations, diffractive cross sections both in pp and pA runs. • Common runs already collecte with a common CMS/TOTEM trigger. • Possibility to repeat the multiplicty and diffractive cross section • measurements when central jets are produced. • Siena, 21 December 2012 M. Berretti 24

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