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

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Presentation on theme: "Giornata del dipartimento di Fisica M. Berretti Siena, 21 December 2012 Latest results from the TOTEM experiment The TOTEM experiment Physics results Ongoing."— Presentation transcript:

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 Stand-Alone: - TOT pp with a precision ~ 1-2% ( L ind. meth.) simultaneously measuring : N el down to -t ~10 -3 GeV 2 and N inel with losses < 3% - Elastic pp scattering in the range < |t| ~ (p ) 2 < 10 GeV 2 - Soft diffraction (SD and DPE) - Particle flow in the forward region (cosmic ray MC validation/tuning) TOTEM Physics Program Overview Siena, 21 December 2012 M. Berretti 3 pp elastic, inelastic and total cross section Forward multiplicities Diffractive processes (SD) Large rapidity (-ln tan /2) gap

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

5 ATLAS A Toroidal LHC ApparatuS LHCf LHC forward experiment LHCb The Large Hadron Collider beauty experiment ALICE A Large Ion Collider Experiment TOTEM is composed by 3 different detectors: T1: CSC chambers, charged particle tracking 18< <90 mrad T2: GEM chambers, charged particle tracking 3< <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). The TOTEM experiment at the LHC Siena, 21 December 2012 M. Berretti 5

6 The RP detector Beam 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 Physical Edge 10% Efficiency90% Efficiency One Roman Pot Sensitivity up to 50 m thanks to the Current Terminating Structure Siena, 21 December 2012 M. Berretti 6

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

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

9 40 Triple Gas Electron Multiplier chambers Installation of 2 T2 quarters Sensitive Area Δϕ=192 o Advantage of a GEM plane : High tolerance to radiation (> 50 Mrad) High rate capability (> 10 MHz/cm 2 ) Low material budget (10 planes: 0.07 X 0 ) The large occupancy and the impossibility to resolve the pile-up vertices make T2 usable only for low luminosity runs The T2 detector Siena, 21 December 2012 M. Berretti 9 Drift Transit Induction GEM foil Readout Plane

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

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

12 Total cross section 7 TeV in 3 ways Luminosity calibration: 1) L= 82/ b ± 4% L= 83.7/ b ± 3.8% 2) L= 1.65/ b ± 4% L= 1.65/ b ± 4.5 % Estimated by CMS Estimated by TOTEM 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 EPL 96 (2011) To be published d σ EL /dt [mb/GeV 2 ] -t [GeV 2 ] Needs the extrapolation of the elastic rate to t=0 Obtained in a low luminosity run at *=90m optics where RP edge approaches at 5 to the beam center. A = 506 ±22.7 syst ±1.0 stat mb/GeV 2 B = 19.9±0.26 syst ±0.04 stat GeV -2 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. inel : 72.9 ± 1.5 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% el = 25.1±1.1 mb Needs the value of Needs the value of (From the COMPETE collaboration fit, = 0.14, later with a direct measurement at *=1Km ) Siena, 21 December 2012 M. Berretti 13

14 NB: Low mass diffraction cross-section can be constrained Estimation of σ inel = σ tot – σ el = 73.2± 1.3mb can be done with RP-only measurement (L-dependent). However, T1+T2 visible σ <6.5 inel = 70.9 ± 2.8 mb σ >6.5 inel = 3.7% σ <6.5 inel 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. inel : 72.9 ± 1.5 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% EL = 25.1±1.1 mb inel T2VIS = 95% inel inel T2VIS = 95% inel el = 25.1±1.1 mb Siena, 21 December 2012 M. Berretti 14

15 T1+T2 (3.1 < | | < 6.5) give an unique forward charged particle LHC lower M diff reachable: minimal model dependence on required corrections for low mass diffraction Mx < 3.4 GeV = 3.1 ± 1.5 mb M X > 3.4 GeV/c 2 SD d SD /d SIBYLL/PYTHI A8 QGSJET-II-4 S. Ostapchenko arXiv: v2 [hep-ph] 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 Low mass diffraction: T1+T2 acceptance Siena, 21 December 2012 M. Berretti 15 (M x 2 s )

16 July 2012: runs at * = 90 m inel = mb Siena, 21 December 2012 M. Berretti 16 Cross section 8 TeV - N el / N inel = tot = mb Same analysis strategy as for the 7 TeV with the luminosity independent method:

17 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 p CR -p AIR collisions with p CR of ~25 PeV. The CR connection: tuning of the MC generator used in the Extensive Air Showers simulations Forward Physics: importance of the dN/d measurement Siena, 21 December 2012 M. Berretti 17

18 Forward Physics: importance of the dN/d measurement Observation of the extended longitudinal scaling: p-Gold collisions 130 GeV 19.6 GeV 200 GeV approach to a limiting distribution which doesnt depend anymore on the collision center of mass energy. For very high energy collisions in the reference system with the target at rest, particles produced in the fragmentation region approach to a limiting distribution which doesnt depend anymore on the collision center of mass energy. 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 Published: EPL 98 (2012) TOTEM measurements combined with the other LHC experiments TOTEM measurements compared to MC predictions 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: nel 95% inel - Diffractive events with M Diff > 3.4 GeV - ND events > 99% Siena, 21 December 2012 M. Berretti 19 Measurement of the dN CH /d in T2

20 Date, SetTriggerInelastic events RP position July 7, DS 2T2 || RP 2arms || BX~2 M 6 July 12-13, DS 3aT2 || RP 2arms || BX~10 M 9.5 V, 11 H July 12-13, DS 3bT2 || RP 2arms || CMS (CMS = 2 pT > 20GeV, 2, 2 central e/ ~3.5 M 9.5 V, 11 H tot, nel with CMS, soft & semi-hard diffraction, correlations DateTriggerInelastic events May 1T2 || BX~5 Mno RP dN/d, correlations, underlying event May 2012: low pileup run: * = 0.6 m, s 1/2 = 8 TeV, T1 & T2 & CMS read out July 2012: * = 90 m, s 1/2 = 8 TeV, RP & T1 & T2 & CMS read out 2011 Ion run: proof of principle 2012: 1 st realization of common running CMS & TOTEM trigger exchange Offline data synchronization (orbit and bunch #) + merging (n-tuple level) Joint data taking with CMS Siena, 21 December 2012 M. Berretti 20

21 TOTEM analyses in progress Inelastic dN CH 8 TeV CMS + T2 (0 < | | < 6.5) Inelastic dN CH /d T1 7 TeV (3.1 < | | < 4.7) Inelastic dN CH 8 TeV with the displaced vertex (11m) Double Pomeron exchange cross section (soft and hard), exclusive jet production in CMS in double pomeron exchange Differential cross section measurement for single diffraction d S D /dt and double diffraction d DD /d min Double Diffraction Single Diffraction Double Pomeron Exchange Multiplicities Diffractive studies Main final state topology for inelastic events 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 = fine structure constant = relative Coulomb- nuclear phase G(t) = nucleon el.-mag. form factor = (1 + |t| / 0.71) -2 Total (Coulomb & nuclear) Nuclear scattering dominant Coulomb-Nuclear interference Coulomb 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 (s 1/2 NN =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. The TOTEM experiment at LHC is fully operative. 7 analysis-papers have been published/submitted (on the elastic, 7 analysis-papers have been published/submitted (on the elastic, inelastic, total pp cross and 8 TeV and on the T2 dN/d inelastic, total pp cross and 8 TeV and on the T2 dN/d 7 TeV) 7 TeV) Fundamental contribution of the Siena University to this Fundamental contribution of the Siena University to this success (installation and commissioning of T2, TOTEM-trigger, success (installation and commissioning of T2, TOTEM-trigger, T2 offline and online software...). T2 offline and online software...). Sevaral analyses are ongoing: Sevaral analyses are ongoing: Large amount of work done (to do) on analysis of the multiplicties, Large amount of work done (to do) on analysis of the multiplicties, correlations, diffractive cross sections both in pp and pA runs. correlations, diffractive cross sections both in pp and pA runs. Common runs already collecte with a common CMS/TOTEM trigger. Common runs already collecte with a common CMS/TOTEM trigger. Possibility to repeat the multiplicty and diffractive cross section Possibility to repeat the multiplicty and diffractive cross section measurements when central jets are produced. measurements when central jets are produced. Siena, 21 December 2012 M. Berretti 24


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