The TOTEM Experiment at the LHC Giuseppe Latino

The TOTEM Experiment at the LHC Giuseppe Latino (University of Siena & Pisa INFN) (on behalf of the TOTEM Collaboration) Rencontres de Moriond – QCD & HEI La Thuile – March 20, 2009 Physics program Ø Detector overview Ø 1/16

TOTEM @ CERN Large Hadron Collider (LHC) LHC - p-p collisions at s =14 Te. V - Linst up to ~ 1033 cm-2 s-1 - start up ~ Fall 2009 - 6 experiments CMS TOTEM - Total Cross Section - Elastic Scattering - Diffractive Dissociation Total and Elastic Measurement TOTEM Collaboration: Bari, Budapest, Case Western Reserve, CERN, Genova, Helsinki, Penn State, Pisa/Siena, Prague, Tallin (~ 80 physicists) Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 2/16

TOTEM & CMS @ IP 5 Leading Protons measured at -147 m & -220 m from IP Ca st or (C MS ) CM T 2 Leading Protons measured at +147 m & +220 m from IP S T 1 TOTEM Experiment T 1 T 2 Leading protons: RPs at 147 m and 220 m Rap gaps & Fwd particle flows: T 1 & T 2 telescopes Fwd energy flows: Castor & ZDC (CMS) Moriond QCD & HEI – March 20, 2009 Ca st or (C MS ) G. Latino – The TOTEM Experiment at the LHC 3/16

TOTEM Physics Program Overview Stand-Alone - �TOTpp with a precision ~ 1 -2%, simultaneously measuring: Nel down to -t ~10 -3 Ge. V 2 and Ninel with losses < 3% - Elastic pp scattering in the range 10 -3 < |t| ~ (p�)2 < 10 Ge. V 2 - Soft diffraction (SD and DPE) - Particle flow in the forward region (cosmic ray MC validation/tuning) 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 Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 4/16

Total Cross Section �PP Current models predict at �s = 14 Te. V: �PP = 90 - 130 mb TOTEM goal: absolute error ~ 1 mb (Linst ~ 1028 cm-2 s-1) �possibility to distinguish COMPETE Coll. [PRL 89, 201801 (2002)] among different models (~ ln 2 s ) Luminosity independent method: - elastic scattering (down to |t| ~ 10 -3 Ge. V 2) - inelastic scattering �proper tracking acceptance in forward region required Optical Theorem: � Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 5/16

Elastic Scattering Cross Section d�PPel/dt Coulomb int. : CKL formula Photon - Pomeron interference Multigluon (“Pomeron”) exchange e– B |t| N Events/Ge. V 2 (BSW) t p 2 2 Predicted at LHC: Diffractive structure �elpp ~ 18 - 35 mb Wide range of predictions; big uncertainties at large |t|; whole |t| range measured with good statistics. p. QCD ~1 day (1) (2) Allowed |t| range depends onshort runs 28)cm -2 s-1 required 2 Dedicated at =high-� (and Lreduced � are for precise (1) * 1540 m*(typical ): |t|min = 0. 002 Ge. V inst = 1. 0 x 10 beam optics of the(2) -2 s-1): |t| 2 �* = 90 m (typical Linstof = 1. 0 x 1030� cmrad measurement scattering angles a few min = 0. 04 Ge. V Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 6/16

Running Scenarios Scenario Physics: 1 low |t| elastic, tot (@ ~1%), MB, soft diffr. 2 low/large |t| elastic, tot (@ ~5%), MB, soft/semi-h. diffr. 3 large |t| elastic, hard diffraction * [m] 1540 90 2 0. 5 N of bunches 43 156 936 2808 Bunch spacing [ns] 2025 525 25 N of part. per bunch (0. 6 1. 15) x 1011 1. 15 x 1011 Half crossing angle [ rad] 0 0 92 Transv. norm. emitt. n [ m rad] 1 3. 75 RMS beam size at IP [ m] 450 213 32 RMS beam diverg. at IP [ rad] 0. 3 2. 3 16 Peak Luminosity [cm-2 s-1] 1028 2 x 1029 3 x 1030 1033 Cross section beam ang. spread at IP: * = ( / �*) beam size at IP: * = ( *) Luminosity * (m) 1540 90 2 L (cm-2 s-1) 1033 1029 1030 1032 TOTEM runs Standard runs Accessible physics depends on luminosity & � * Moriond QCD & HEI – March 20, 2009 0. 5 Optimal �* = 1540 m optics requires special injection optics: probably NOT available at the beginning of LHC ‘Early’ �* = 90 m optics achievable using the standard LHC injection optics G. Latino – The TOTEM Experiment at the LHC 7/16

Combined Uncertainty in �tot �* = 90 m 1540 m Extrapolation of elastic cross-section to t = 0: ± 4% ± 0. 2 % Total elastic rate (strongly correlated with extrapolation): ± 2% ± 0. 1 % Total inelastic rate: (error dominated by Single Diffractive trigger losses) ± 1% ± 0. 8 % Error contribution from (1+� 2): (using full COMPETE error band d�/�= 33 %) Þ ± 1. 2 % Total uncertainty in �tot including correlations in the error propagation: * = 90 m : ± 5% * = 1540 m : ± (1 ÷ 2) % Slightly worse in L (~ total rate squared) : ± 7 % (± 2 %) Precise with = 1540� m requires: � * = 90 Measurement m required for�*early tot measurement during the first improved knowledge of optical alignment precision < 50 �m year of LHC running at �functions; s = 10 Te. V Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 8/16

CMS/TOTEM Common Physics Program T 1, T 2 Charged particles Roman Pots d. Nch/d LHC, inelastic collisions CMS ~ 60 mb Elastic Scattering 18 - 35 mb d. E/d Energy flux Single Diffraction TOTEM+CMS 10 - 16 mb M CMS 4 - 14 mb Double Diffraction 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 Moriond QCD & HEI – March 20, 2009 Double Pomeron Exchange M G. Latino – The TOTEM Experiment at the LHC 0. 2 - 1. 5 mb << 1 mb 9/16

Early TOTEM Measurents (p = 5 Te. V, �* = 3 m) Roman Pots • Sing. Diff. (horizontal RPs): Acceptance: 0. 02 < �= �p/p < 0. 18 Resolution: �(�) ~ 1 � 6 · 10 -3, �(�) ~ 15 �rad d�SD/d. M at high masses, 1. 4 < M < 4. 2 Te. V, �(M)/M < 10 % SD • DPE (horizontal RPs): d�DPE/d. M at high masses, 0. 2 < M < 1. 8 Te. V, �(M)/M < 10 % DPE • El. Scatt. (vertical RPs): d�ES/dt for 2 < |t| < 10 Ge. V 2, �(t)/t ~ 0. 2/�|t| ND SD T 1/T 2 • Charged multiplicity studies (min. bias and cosmic ray MC generators tuning/val. ) • Rapidity gap studies (topologies of diffr. events) Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 10/16

TOTEM Detectors: Setup in CMS Inelastic Telescopes: Detectors on both sides of IP 5 reconstruction of tracks and interaction vertex; trigger capability with acceptance > 95 % T 1: 3. 1 < < 4. 7 CMS T 2: 5. 3 < < 6. 5 � T 1: 18 - 90 mrad T 2: 3 - 10 mrad = - log(tg(�/2)) HF HF 10. 5 m T 1 ~14 m T 2 Elastic Detectors (Roman Pots): position of p scattered elastically at small angles Active area up 1 -1. 5 mm from beam: 5 -10 �rad RP 220 RP 147 ZDC Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 11/16

Roman Pots 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 at 10�+ d from beam (�beam ~ 80�m at RP) Beampipes Each RP station has 2 units, 4 m apart. Each unit has 2 vertical insertions (‘pots’) and 1 horizontal �‘Edgeless’ detectors to minimize d Horizontal Pot: extend acceptance; overlap for relative alignment using common track. Absolute (w. r. t. beam) alignment from beam position monitor (BPM) Moriond QCD & HEI – March 20, 2009 Horizontal Pot G. Latino – The TOTEM Experiment at the LHC Vertical Pot BPM 12/16

Roman Pots Each Pot: 200�m thick beam 10 planes of Si detectors 512 strips at 45 o orthogonal Pitch: 66 �m Total ~ 5. 1 K channels Digital readout (VFAT): trigger/tracking Resolution: �~ 20 �m Integration of traditional Voltage Terminating Structure with the Current Terminating Structure Readout chip VFAT Edgeless Si detector: 50 μm of dead area Moriond QCD & HEI – March 20, 2009 Detectors expected to work up to Lint ~ 1 fb-1 Installation ongoing: RP 220 (147) m fully (partially) equipped by June G. Latino – The TOTEM Experiment at the LHC 13/16

T 1 Telescope Each arm: 3 m 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. 5 K ch. Resolution: ~ 1 mm 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-2 s-1 Installation foreseen for May/June (if necessary also in September) 1/4 of T 1 Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 14/16

T 2 Telescope Each arm: strips 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 for R, f Trigger from Pads (1560/chamber) Digital readout (VFAT) for ~ 41. 4 K ch. Resolution: R ~ 100 m, ��~ 1 o pads T 2 Triple GEM technology adequate to work at least 1 yr at L=1033 cm-2 s-1 Installation ongoing: Test fully Beam done by May Moriond QCD & HEI – March 20, 2009 GEM Technology: T 2: “GEM” Technology � Gas Detector Rad-hard High rate Good spatial and timing resolution Castor Calorimeter (CMS) ~ 0. 4 m G. Latino – The TOTEM Experiment at the LHC 15/16

Summary & Conclusions TOTEM will be ready for data taking at the LHC restart and will run under all beam conditions. Measurement of total pp cross-section (and L) with a precision of 1 -2% (2%) with �* = 1540 m (dedicated runs). Measurement of elastic scattering in the range 10 -3 < |t| < 10 Ge. V 2 Early measurements § § low �*: - study of SD and DPE at high masses - elastic scattering at high |t| - measurement of forward charged multiplicity �* = 90 m: - first measurement of �tot (and L) with a precision of ~ 5% (~ 7%) - elastic scattering in a wide |t| range - inclusive studies of diffractive processes - measurement of forward charged multiplicity Later: common CMS/TOTEM Physics Programme Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC 16 16/16

Ba up ck es id Sl Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC

Determination of d�/dt at t=0 Model dependent uncertainty due to Coulomb interferences Very approximate formula: West and Yenneie model for Coulomb-Nuclear interference (�(t) = const) Coulomb scattering Coulomb. Nuclear interference Nuclear scattering - - - BSW = fine structure constant f = relative Coulomb-nuclear phase G(t) = nucleon em form factor = (1 + |t|/0. 71)-2 a = Re/Im f(p�p) Measurement of the exponential slope B in the t-range 0. 002 - 0. 2 Ge. V 2 needs beams with tiny angular spread �large * Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 1

Possibilities of �measurement asymptotic behaviour: µ 1 / ln s for s � � pred. ~ 0. 13 at LHC Try to reach the Coulomb region and measure interference: • • move the detectors closer to the beam than 10 + 0. 5 mm run at lower energy @ √s < 14 Te. V La Thuile – March 1, 2008 G. Latino – The TOTEM Experiment at LHC B 2

Details on Optics Proton transport equation: x = Lx x* + vxx* + D * * y = L y� y + v yy Optical functions: �= � p/p; t = tx + ty; ti ~ -(p�i*)2 (x*, y*): vertex position at IP ( x*, y*): emission angle at IP - 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) Example sample of diffractive protons at different �* - low �*: p detected by momentum loss (�) - high �*: p detected by trans. momentum (ty) Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 3

Optical Functions (�* = 90 m) L = ( *)1/2 sin(� (s)) (m) v = (� / *)1/2 cos( (s)) Idea: Ly large Lx=0 vy = 0 y(220) = /2 x(220) = (parallel-to-point focussing on y) x = L x x +D *+ vx x* * * y = L y� y + v yy �= � p/p (x*, y*): vertex position at IP ( x*, y*): emission angle at IP t = t x + ty ti ~ -(p�i*)2 Moriond QCD & HEI – March 20, 2009 hit distribution (elastic) 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 21 G. Latino – The TOTEM Experiment at the LHC B 4

Roman Pots Acceptances x resolved RP 220 m L = 1028 – 2 x 1029 95% of all p seen; all x * = 90 m L = 1029 – 3 x 1030 65% of all p seen; all x * = 0. 5 – 2 m L = 1030 – 1034 p with x > 0. 02 seen; all t Acceptanc e = 0. 5 m - 2 m * = 1540 m Elastic Scattering (RP 220) *=1540 m *=90 m *=2 m Detector distance to the beam: 10 +0. 5 mm * = 1540 m -t = 0. 01 Ge. V 2 -t = 0. 002 0. 06 4. 0 Ge. V 2 Beam log(-t / Ge. V 2) Det. dist. 1. 3 mm Moriond QCD & HEI – March 20, 2009 6 mm G. Latino – The TOTEM Experiment at the LHC B 5

Measurement of �TOT at 1% Loss at low masses Pythia generator simulated extrapolated Acceptance detected Trigger Losses (mb): (mb) Double arm T 1/T 2 Single arm T 1/T 2 Uncertainty after Extrapolation (mb) Minimum bias 58 0. 3 0. 06 Single diffractive 14 - 2. 5 0. 6 Double diffractive 7 2. 8 0. 3 0. 1 Double Pomeron 1 - - 0. 02 Elastic Scattering 30 - - 0. 1 ��T/�T ~ �[(0. 006)2 Inelastic + Moriond QCD & HEI – March. Elastic 20, 2009 Error + (0. 002)2 Extrapolation t=0 Error + (0. 012)2] Total 0. 8% ~ 0. 014 Error on r B 6

Forward Physics: VHE Cosmic Ray Connection Total multiplicity in T 2 (5< <7) p-p collisions @ LHC as predicted by generators tipically used to model hadronic showers generated by VHE CR Interpreting cosmic ray data depends on hadronic simulation programs. Forward region poorly known/constr. Models differ by factor 2 or more. Need forward particle/energy measurements e. g. d. N/d�, d. E/d�… Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 7

Expected Radiation Dose in CMS/TOTEM In 1 year @ Linst = 1034 cm-2 s-1 At RPs locations => Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 8

Si CTS Edgeless Detectors for Roman Pots Planar technology with CTS (Current Terminating Structure) I 1 current terminating ring I 2 biasing ring Al + Si. O 2 p+ p+ n-type bulk cut edge Al 50µm bias gard/clean-up ring (CR) AC coupled microstrips made in planar technology with novel guard-ring design and biasing scheme Integration of traditional Voltage Terminating Structure with the Current Terminating Structure 50 µm n+ 50 μm of dead area Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 9

T 1 Cathode Strip Chamber (CSC) Cathode strips – 5 mm pitch Anode wires – 3 mm pitch Detector design similar to CMS CSC muon chamber Gas Mixture Ar/CO 2/CF 4 Max size: ~ 1 m x 0. 68 m Gas gap: 10 mm Anode wires: � 30�m, 3 mm pitch Cathode strips: 4. 5 mm width, 5 mm pitch Digital readout (VFAT) Ageing studies at CERN Gamma Irradiation Facility: no loss of performance during 12 -month test, with ~0. 07 C/cm accumulated charge on wires corresponding to a dose equivalent to ~ 5 years at L=1030 cm-2 s-1 Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 10

Gas Electron Multiplier (GEM) Ions GEM Technology Developed at CERN (F. Sauli ~ 1997) Used in COMPASS, LHCb, … Gas Detector “Rad-hard”, high rate, good spatial and timing resolution Electrodes: 50 �m kapton + 2 x 5 �m Cu Density: 50 -100 holes/mm 2 Electrons T 2 GEM: Electric field (channel) ~ 100 KV/cm (Vgem = 500 V) �electron cascade Gain: 10 - 100 70 µm 5 µm Cu 50 µm Kapton 140 µm 55 µm 70 µm Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 11

Digital R/O pads VFAT for Trigger 17 VFAT / module T 2 Triple-GEM Detectors Cooling strips HV Divider Gas in/out pads Ar/CO 2 70/30 gas mixture Operating gas gain M = 8000 Digital readout (VFAT) T 2 Triple GEM technology adequate to work at least 1 yr at L=1033 cm-2 s-1 Moriond QCD & HEI – March 20, 2009 Pads: 65( ) x 24( = 1560 pads x = 0. 06 x 0. 018 ~2 x 2 mm 2 - ~7 x 7 mm 2 Strips: 256 x 2 (width 80 m, pitch 400 m) G. Latino – The TOTEM Experiment at the LHC B 12

Totem Electronics VFAT Chip Developed at CERN by the Micro- Electronics group 128 channels of tracking front- end with digital storage and data transmission 8 programmable trigger outputs Designed for radiation tolerance Standardization for all detectors: identical front-end electronics (VFAT chips); identical DAQ and trigger cards Moriond QCD & HEI – March 20, 2009 G. Latino – The TOTEM Experiment at the LHC B 13