Diffraction at LHC - Experimental set-up Risto Orava University of Helsinki and Helsinki Institute of Physics 0.1 Low-x Workshop Antwerpen R.Orava 17. September 2002

Baseline design Criteria of ATLAS & CMS aim at discoveries at high p T Detection of High p T Objects: Higgs, SUSY,... Precise measurement of e, , , , and b-jets: tracking: |  | < 2.5 calorimetry with fine granularity: |  | < 2.5 muon system: |  | < 2.7 Measurement of jets, E T miss : calorimetry extension: |  | < 5 Precision physics (cross sections...): energy scale: e &  0.1%, jets 1% absolute luminosity vs. parton-parton luminosity via ”well known” processes such as W/Z production? 0.2 All this complements the forward physics agenda. Low-x 2002 Risto Orava

Important part of the phase space is not covered by the baseline designs. Much of the large energy, small transverse energy particles are missed. In the forward region (|  > 5) few particles with large energies/small transverse momenta. Charge flow Energy flow 0.4

How to extend baseline LHC experiments for the benefit of forward physics? 1.1 (1) Leading proton & inelastic activity (2) Upgrade scenarios & Forward detectors: ATLAS + A Foward Spectrometer CMS + TOTEM Roman Pots and MicroStations (3) Physics Performance: Diffractive Processes (4) Outlook (TOTEM is accepted to go for a TDR) Low-x 2002 Risto Orava

LHC low  * optics (  * = 0.5m, v6.3) Beam size is small between s= m. Beam dispersion (D x ) large at s>300m: horizontal deviation from the nominal beam position given as:  x =  D x xx s (m) D x (m) Low-x 2002 Risto Orava

LHC optics (v6.3) layout: Two studies end up with a similar detector lay-out Optimized detector locations: 90m, 150m, 180m, 210m, 240m, >400m? Totem Low-x 2002 Risto Orava

Thin window (3 x 2 cm 2 ) TOTEM : Roman Pots for leading protons Concave bottom The detectors approach the beam vertically (step motor) Si-detectors operated at 130K (where the Lazarus effect (V.Palmieri et al.) optimizes charge collection efficiency, reduces noise and provides radiation hardness.) Cryogenic Si-detectors located here (RD39) cm SAB 3. June 2002 Risto Orava  1m

Beam sizes and effective distances at detector locations define the acceptance. LocationBeam sizeEffective distance s(m)  x (mm)  eff (mm) (13) (9) (5) (2.4) (7) In defining  eff, we assume: 10  x (20  x ) Note: beam halo rates difficult to predict at 240m’s For the RF shielding & guard ring add 1mm dead space Low-x 2002 Risto Orava

CMS has reserved space for the forward detectors in T1 and T2 regions CMS SAB 3. June 2002 Risto Orava 3.1

Design of the Forward Spectrometer is Challenging since one has to: operate close to the beam in intense radiation environment meet the constraints due to limited amount of space available integrate the detectors with the machine requirements (vacuum, RF,...) adapt to changing machine conditions (injection, special runs) require movable detectors 3.2 SAB 3. June 2002 Risto Orava These requirements are common to Roman pots, Velo etc. detectors designed to operate within the LHC vacuum chamber.

A novel detector for measuring the leading protons - the Microstation - is designed to comply with the LHC requirements. a compact and light detector system (secondary particle emission, dimensions < 20cm, weight < 2kg) integrated with the beam vacuum chamber (acceptance) geometry and materials compatible with the machine requirements (dynamic vacuum (outgassing atm, bake-out to 180 C), RF impedance (< 0.6m  /ms), em pick-up)  m accurcay in sensor movements (alignment) robust and reliable to operate (access limitations) Si strip or pixel detector technology (heat dissipation (< 50 mW), simplicity & radiation hardness (n flux 10 5 kHz/cm 2, 0.25  m CMOS read-out chips fully functional up to 30Mrad)) 4.1 ©M.Ryynänen, R.O. et al. low-x 2002 Risto Orava

Microstation - initial design

Interface side Emergency trigger Electrical connectors - feed throughs Cooling connectors - circular 4.3 beam 19cm Helsinki group/M. Ryynänen, R.O. et al. Micro- Station low-x 2002 Risto Orava

Inner tube for rf fitting Inch worm motor Emergency actuator Detector Space for cables and cooling link Space for encoder 4.4 6cm Microstation Helsinki group/M. Ryynänen, R.O. et al. Low-x 2002 Risto Orava

Leading Proton Acceptance - High  *(=1100m) 1-x L -t (GeV 2 ) 15  10  Acceptance > 50% for all values of -t:  > 0.03 (0.02) Acceptance > 50% for all values of  : -t > 0.02 GeV 2 Helsinki group/L.Salmi et al. Low-x 2002 Risto Orava

Proton acceptances at 210 & 425m Acceptance limited to  > 0.03 Acceptance to  > low  * (  * = 0.5m) Helsinki group/ S. Tapprogge, K.Österberg et al. - for 20  downgrade by a factor of two low-x 2002 Risto Orava

Detector Support Pitch Adapter APV25 Hybrid Cooling Pipe Spacer A Silicon Detector Module/Totem 6.1

Detecting Higgs Boson in pp  p+X+p P P p1p1 p2p2 p1’p1’ p2’p2’ H M H 2 =  1  2 s In symmetric case (  1 =  2 =  ) for M H = 140 GeV:  = 0.01 (  = 40%)  (pp  p+H+p)  3 fb at  s = 14TeV  M/M  1% Helsinki group/J.Lamsa, R.O. SAB 3. June 2002 Risto Orava

DPE Mass Measurement at 400m Mass resolution vs. central mass assuming  x F /x F = symmetric case: Central Mass (GeV) Mass resolution (GeV)  M = ( ) GeV (  x F /x F = (1-2)  )  65% of the data 20 GeV < M X < 160 GeV (M Xmax determined by the aperture of the last dipole,B11, M Xmin by the minimum deflection = 4mm) 7.6 Helsinki group/J.Lamsa, R.O. SAB 3. June 2002 Risto Orava

- Physics Performance Figures Inelastic activity can be extended to cover (low  *) Charged particles within 3(5.7) < |  |< 7(8.4) Luminosity monitoring for 5.2 < |  |< 6.6 Leading protons can be detected (low  *, >50% efficiency):  > 4  (180m),  > 2.0  (210m),  > (240m),  > 2.0  (300m, 425m) (10  x approach, for 20  x, factor 2 downgrade) Missing mass: For 20 GeV < M X < 160 GeV achieve  1% mass resolution Dedicated runs with  * = 1100m (3500m??): Measure elastic protons down to -t = 4  GeV 2 (240m assumed) Measure diffractive protons down to  > 0.03 (180m) SAB 3. June 2002 Risto Orava

A typical pile-up event A candidate with E T > 50 GeV 1)LVL 1 trigger 2)Pair of protons 3)Pair of jets 4)Kinematic fit 5)3D vx

(1) At LVL 1 Trigger (  < 2.5): Use the minimum combined transverse energy of two central jets E T1 + E T2 > 100 GeV and the difference between the azimuthal angles of the two jets:  1 -  2 = 180 o (within a given cell size of  x  = 0.5 x 20 o ) to suppress the background event rate. A relative suppression of 10 4 (3 kHz LVL 1 trigger rate at L = ) achieved. (2) At a later stage of data collection: Use the measured pair of forward-backward protons to calculate the missing mass: M missing 2 = (p i1 +p i2 -p f1 -p f2 ) 2. Match this with the direct jet-jet effective mass. (3) Investigate the central pair of jets to measure and identify the decay products in a model independent way. Event Selection Strategy 5.7 Helsinki group/J.Lamsa, R.O. SAB 3. June 2002 Risto Orava A model independent analysis of new centrally produced particle states.

Tagging Large E T Jet Pairs Minimum combined transverse energy of two central jets (  < 2.5), E T1 + E T2 = 100 GeV (2) Condition (1) and the difference between the azimuthal angles of the two jets:  1 -  2 = 180 o (within a given cell size of  x  = 0.2 x 10 o and 0.5 x 20 o ) (3) Condition (1) and  E T1 – E T2  < 10 GeV (4) Condition (1) and Condition (2) and Condition (3) As a conclusion: a rejection factor between 10 3 to 10 4 can be obtained by applying the transverse energy based selection on a central pair of jets depending on whether an additional selection on the angular difference between the jet axes is applied or not. 10 Helsinki group/J.Lamsa, R.O.

Requiring two jets (anywhere within |  |<3.2) in the detector, each above the E T threshold given below (size of 0.8*0.8 in  ), the following rates can be expected for : E T >LVL1 rate 20 GeV 40 kHz 40 GeV 6 kHz 60 GeV 2 kHz 80 GeV 0.7 kHz 100 GeV 0.3 kHz i.e. with a rejection factor of one should be well off down to E T  40 GeV cut-off. Preliminary trigger rate analysis 1 : 1 Stefan Tapprogge 11

Upgrade scenarios and Forward detectors - CMS & TOTEM 4.11 The Technical Proposal submitted in 1999 The Technical Design Report (TRD) to be completed by Fall 2002 Designed to co-exist with CMS and to run with large or intermediate  * (1100m & 18m &...) Aims at: Precision measurement of  tot (  tot ~ 1mb) Elastic scattering down to -t min ~ Inclusive (soft) diffractive scattering Forward spectrometer: T1 & T2 for inelastics (3 < |  | < 7) Low-x 2002 Risto Orava