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**LHC/HERA workshop, WG 4 (17. Jan. 2005)**

Startup running of a combined CMS-TOTEM trigger Karsten Eggert CERN, PH Department on behalf of the TOTEM/CMS Collaboration LHC/HERA workshop, WG 4 (17. Jan. 2005)

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T1: 3.1 < h < 4.7 T2: 5.3 < h < 6.5 Optical Theorem

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**CMS + TOTEM: Acceptance**

CMS+TOTEM: largest acceptance detector ever built at a hadron collider > 90 % of all diffractive protons are detected 10 million min. bias events, including all diffractive processes, in a 1 day run with b* = m microstation at 19m ? RPs Total TOTEM/CMS acceptance (b*=1540m) Roman Pots TOTEM+CMS T1,T2 Charged particles dNch/dh Energy flux dE/dh

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Elastic Scattering b* = 1540 m acceptance

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**Elastic Scattering Cross-Section**

Photon - Pomeron interference r Multigluon (“Pomeron”) exchange e– B |t| 104 per bin of 10-3 GeV2 ds/dt [mb / GeV2] t p2 q2 diffractive structure pQCD wide range of predictions pp 14 TeV BSW model -t [GeV2] b* = 1540 m L = 1.6 x 1028 cm-2 s-1 (1) b*=18 m L = 3.6 x 1032 cm-2 s-1 (2) ~1 day (1) (2)

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**Diffraction at high b*: Acceptance**

Leading protons in diffraction characterized by t = p2 q2 and x = Dp / p b* = 1540 m, RP at 220 m: A > 95 % ~ 90 % of all diffractive protons are seen in the Roman Pots (assuming ). % Resolution in x: b* = 1540 m: () = 5 x (L 2.4 x 1029 cm-2 s-1)

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**CMS / TOTEM : ideal detector to study diffractive and forward physics with proton measurements**

Soft and hard diffraction in Single and Double Pomeron Exchange production of jets, W, J/y, heavy flavours, hard photons Excellent proton measurement: gap survival Double Pomeron exchange as a gluon factory Production of low mass systems (SUSY, c ,D-Y,jet-jet, …) Glue balls, … Higgs production ? Structure functions (parton saturation) with and without detected protons Forward physics: DCC, particle and energy flow gg physics Different running scenarios (b* = 1540, 172, 18, 0.5 m)

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**Running Scenarios 1 2 3 4 Scenario Physics: low |t| elastic,**

stot , min. bias, soft diffraction 2 diffraction 3 large |t| elastic 4 hard diffraction b* [m] 1540 18 172 N of bunches 43 156 2808 N of part. per bunch 0.3 x 1011 ( ) x 1011 1.15 x 1011 Half crossing angle [mrad] 150 Transv. norm. emitt. [mm rad] 3.75 RMS beam size at IP [mm] 454 95 294 RMS beam diverg. [mrad] 0.29 5.28 1.7 220 m [GeV2] 2 x 10-3 1.3 2 x 10-2 220 m [GeV2] 0.6 7 Peak luminosity [cm-2 s-1] 1.6 x 1028 2.4 x 1029 3.6 x 1032 (1 -4) x 1031

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**New optics b*=172 m Ly large (~270 m) tmin =2 x 10-2 GeV2**

~90% of all diffractive protons are seen Lx ~ 0 q independent Vertex measured by CMS x determination with a precision of few 10 -4

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tmin ~ 2 x 10-2 GeV2 10 s beam

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**Conclusion on new optics (b*=172 m) - preliminary**

Luminosity of 4 x 1031 cm-2 s-1 About 90% of diffractive protons are seen in the RP at 220 m x resolution of few to 10 -3 q resolution of few mrad Future: more detailed studies on acceptance and resolution further optimization towards higher luminosity

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**Level-1 Trigger Schemes for min. bias physics**

(L = 1.6 x 1028 cm-2 s-1) RP CMS RP Elastic Trigger: Signal: Hz Background: 20 Hz Single Diffractive Trigger: Signal: Hz Background: < 1 Hz ? (using vertex reconstruction in T1/T2) Double Diffractive Trigger: Signal: Hz Central Diffractive Trigger: Signal: Hz Background: Hz Minimum Bias Trigger: Signal: kHz Backgrounds under study! T1/T2 p p p p

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**Runs with ~90% detection of diffractive protons**

Initial several one day runs with b* = 1540 m and 43 bunches L = 1.6 x 1028 cm-2 s-1 10 8 min. bias events / day 1000 events / mbarn per day Trigger combinations: CMS min bias, T1, T2, forward protons b* = 1540 m and 156 bunches L = 2.4 x 1029 cm-2 s-1 20 events / nbarn per day central diffraction: p left x p right x central activity single diffraction: (T1, T2, CMS forward cal.) left x p right heavy flavours, jets : low pt leptons, min jets b* = 172 m and 2808 bunches L = 4 x 1031 cm-2 s-1 3000 events / nbarn per day Trigger combinations: low pt leptons, jets, diffr. protons

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**Exclusive Production by DPE: Examples**

Advantage: Selection rules: JP = 0+, 2+, 4+; C = +1 reduced background, determination of quantum numbers. Good f resolution in TOTEM: determine parity: P = (-1)J+1 ds/df ~ 1 +– cos 2f Particle sexcl Decay channel BR Rate at 2x1029 cm-2 s-1 1031 cm-2 s-1 (no acceptance / analysis cuts) c0 (3.4 GeV) 3 mb [KMRS] g J/y g m+m– p+ p– K+ K– 6 x 10-4 0.018 1.5 / h 46 / h 62 / h 1900 / h b0 (9.9 GeV) 4 nb [KMRS] g U g m+m– < 10-3 0.07 / d 3 / d H (120 GeV) 0.1 100 fb assume 3 fb bb 0.68 0.02 / y 1 / y Higgs needs L ~ 1033 cm-2 s-1, i.e. a running scenario for b* = 0.5 m: try to modify optics locally, try to move detectors closer to the beam, install additional Roman Pots in cold LHC region at a later stage.

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**High luminosity runs (b*=0.5m) with x>2.5%**

L = 0.5 x 1033 cm-2 s-1 Trigger condition 1: jets and leptons x p left x p right Trigger condition 2 : jets and leptons x p left x gap right define the trigger thresholds: 2 jets with pt > 40 GeV for the Higgs 2 large pt jets for high mass central diffraction

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**Higgs event Characteristics: dN/dt & xmin **

xmin < 0.3% for one side trigger with x max > 2.5% Totem acceptance -t < 1 GeV2 x acceptance? DPE PHOJET (MH = 120 GeV) DPE PHOJET (MH = 120 GeV) dN/dt dN/dxmin -t (GeV2) xmin SN/dt SN/dxmin -t (GeV2) xmin dN/dt exp(6t) should detect p’s down to x 10-3

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**Event Characteristics:**

Where do the decay b-jets go? Asymmetric pair of protons A typical – symmetric - pair of protons DPE PHOJET (MH = 120 GeV) DPE PHOJET (MH = 120 GeV) dN/dhbmax dN/dhbmax xpmin 0.002 xpmax 0.02 Symmetric pairs dominate Asymmetric pair of protons hbmax hbmax SN/dhbmax SN/dhbmax xpmax 0.02 xpmin 0.002 hbmax hbmax All the b-jets are confined within h 5.

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**Detection Prospects for Double Pomeron Events**

In collaboration with CMS p1’ p1 b* = 1540 m: = 0.5% L 2.4 x 1029 cm-2 s-1 b* = 172 m : ~ few L ~ cm-2 s-1 b* = 0.5 m: ~ 1 ‰ L ~ cm-2 s-1 P M2 = x1 x2 s P Dy = – ln x ymax = 6.5 p2 p2’ b* = 0.5 m p dN/dy p – ln x1 – ln x2 CMS + TOTEM CMS Trigger via Roman Pots x > 2.5 x 10-2 Trigger via rapidity gap x < 2.5 x 10-2 y

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**Double Pomeron Exchange: Cross-Section**

sDPE = 0.5 – 1 mb (1–2) x 107 events per day at b* = 1540 m, L = 2 x 1029 cm-2 s-1 Events / GeV 10-1 2x 10-2 2x 10-3 2x 10-4 10-5 10-6 200 ~ 1 day (3) , (4) L = 2x1029, 1031 cm-2s-1 [e from Pomeron trajectory a(t) = 1 + e + a’ t ]

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