Andrew Brandt – September 19 2003 Small-x 2003 – 1

Forward Physics with Forward Physics with ATLASATLAS

• Luminosity measurement for ATLAS• Forward Physics with ATLAS

D.Bocian, M.Boonekamp, A.Brandt, E.Brash, B.Caron, K.De, I.Efthymiopoulos, A.Faus-Golfe, P.Grafstrom, W.Guryn, M.Haguenauer, A.Hamilton, V.Hedberg, B.Jeanneret, J.Lamsa, C.Leroy, M.Lokajicek, G.Lolos, J-P.Martin, J.McDonald,

Z.Papandreou, J.Pinfold, M.Rijssenbeek, E.Rosenberg, V.Simak, J.Soukup, H.Takai, V.Telnov, S.Tapprogge, W.Turner, S.Valkar, J.Velasco, A.Verdier, S.White, Y.Yao

Thanks to:Michael Rijssenbeek for his slides!

.

Andrew Brandt – September 19 2003 Small-x 2003 – 2

Luminosity MeasurementLuminosity Measurement• Goals of the ATLAS Luminosity and Forward Physics

Group:– Measure L with ≲2% accuracy– Study opportunities for diffractive physics with ATLAS

• Most important LHC characteristics: Luminosity L and CM Energy s

• Luminosity measurement needed for:– Precision comparison with theory:

• e.g.: bb, tt, W/Z, jet, …, H, SUSY, …• Cross section gives additional info

– Precision comparison with other expt’s• Luminosity from:

– LHC Machine parameters (~5-10%)– Rates of well-calculable processes

• Dedicated Luminosity monitor: LUCID

Relative precision on the measurement of HBR for various channels, as function of mH, at Ldt = 300 fb–1. The dominant uncertainty is from Luminosity: 10% (open symbols), 5% (solid symbols).

(ATL-TDR-15, May 1999)

Andrew Brandt – September 19 2003 Small-x 2003 – 3

The ATLAS DetectorThe ATLAS Detector

GeV

10%( , ) 0.3%/

E eE E

GeV

60mrad/E

GeV

4 ns/t E

GeV

50%( ) 3%/

E

E E

GeV

50%( jet) 2%/

E

E E

Calorimetry:

TAS

R

50 1 2 43 6 7 8

Barrel

FCAL LUCIDTracking

EndCapRP

ZDC/TAN

Diffraction/Proton Tagging Region

y109

-chambers

GeV(Inner Det) (0.03 / 1.2)%TT

pp

Tracking:

GeV(IDet+ ) (0.009 / 1.4)%TT

pp

ATLAS has insufficient forward coverage for Total Rate measurement

Andrew Brandt – September 19 2003 Small-x 2003 – 4

Services In/Out

ToUXA

PMTs

Inner radius of LUCID ~7 cm, outer radius ~20cm

~17< |z| <~19 m5.2< || <6.2

LUCID

ATLAS – Luminosity Monitor ATLAS – Luminosity Monitor (J. Pinfold et al.)

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BaselineBaseline• Luminosity with CNI optics and Coulomb Normalization

– Roman Pots at 220-240 m– Scintillating strip detectors– Integrate into L1 Trigger

• LUCID for relative L monitoringDedicated detector:

• bundle of projective Cerenkov cones: 5 layers of 40 tubes each• low mass (6 kg), rad hard, quartz fiber readout

proof of principle: CLC at CDF!

• Cross checks with:– W/Z rates– Double photon exchange production of muon pairs– Elastic slope of dN/dt|t=0 plus machine L– others…

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ExtensionsExtensions• Diffractive cross sections

– need RP pairs at intermediate locations: 90, 150 m– possibly forward calorimetry (TAS region)

• Large-|t| studies (t in dip region and beyond) – need RP pairs at intermediate locations: 90, 150 m and

smaller?

• DPE Higgs production…– need additional RP pairs at cryogenic locations: 330 m, 420 m– forward calorimetry (TAS region) might be attractive…

Andrew Brandt – September 19 2003 Small-x 2003 – 7

Coulomb Normalization of Coulomb Normalization of LLPossible with very high

β* (≥ 2500 m) optics (3500m now dead):

*=3500 m optics: A. Faus-Golfe, M. Haguenauer, J. Velasco, "Luminosity determination using Coulomb scattering at the LHC",

presented at EPAC2002, June 2002

• Normalization of the scattering amplitude at t 0 to the exactly calculable Coulomb amplitude:

determines Luminosity L directly (and measure σtot, ρ0, b, …)

L/L ~ 2% (UA4 experience) • Need closest possible

approach to the beam• Very-small-angle detectors in

Roman Pots UA4

??

LHC

ISR

2

el tot2

el20

0

20

2 ( )4

4

C N

ti

ft

bE

f

t

d d G e i edtdt tt

N

L L L

RHIC

Caveat: Phase and shape of FN(s,t) ! V.Kandrát, M.Lokajíček, PL B 544 (2002) 132.

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Elastic Scattering in CNI Regime Elastic Scattering in CNI Regime • Need: t min tCNI = 8EM/tot 710–4 GeV2

• For εN ≃1106 , kσ=15, t min= pBmp kσ

2εN/* = 610–4 GeV2 * ≳ 2500 m

• Detector: beam size (rms) d = √(βdεN/) , kσ d ≳ 1.5 mm d ≳ 80 m

• Roman Pot detectors between Q5-Q6 or Q6-Q7 (z 220-240 m)– Leff 500 m, =x /Leff, x ∈ {~1.5 mm, 25 mm}

tmin = (pmin)2 4×10–4 GeV2 tmax (pmax)2 0.12 GeV2

– Precision needed: t/t ≃ 1‰ x O(10 m) need “self-calibrating” detectors

L/L 2%• Positions at z >300 m possible, but difficult

240 m 220 m

dN/dt shapeis crucial!

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June Workshop on Roman Pot June Workshop on Roman Pot DetectorsDetectors

• Parallel effort on RP detectors…• Aim: focus on a (single?)

appropriate technology for TOTEM/CMS and ATLAS

http://efthymio.home.cern.ch/efthymio/LHC-LUMI/Workshop03/or via the Luminosity and Forward Physics WG webpage

Andrew Brandt – September 19 2003 Small-x 2003 – 10

Requirements for Roman Pot Requirements for Roman Pot DetectorsDetectors• “Dead space” d0 at detector’s edge near the beam the beam:

d0 ≲ 100 m (full/flat efficiency away from edge)• Detector resolution: d = 30 m (10 m for pleading measurement)• Same d = 30 m (10 m) relative position accuracy between

opposite detectors (e.g. partially overlapping detectors, …)

• Radiation hardness: 100 Gy/yr (105-6 Gy/yr at full L)• Operate with the induced EM pulse from circulating bunches

(shielding, …)

• Rate capability: O(Mhz) (40 MHz); time resolution t = O(ns) • Readout and trigger compatible with ATLAS TDAQ• Other:

– Simplicity, Cost– extent of R&D needed, time scale, manpower, …– issues of LHC safety and controls

Andrew Brandt – September 19 2003 Small-x 2003 – 11

Forward Physics Interest…Forward Physics Interest…Possible extension of ATLAS baseline physics:• (Soft) Diffractive cross sections are large:

el 26 mb, SD DD 13 mb (i.e. close to Pumplin bound!)

– need only modest L

• Elastic and Total cross section measurements: tot, elastic, Re(fN)/Im(fN), del/dt |N

•dip/structure in d/dt at |t|≈0.5 GeV2? •Regge Pomeron & Odderon à la D&L• transition to pQCD at |t| ≈ 8 GeV2

– Roman Pots at 220-240 m

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Single and Double DiffractionSingle and Double Diffraction•Soft Pomeron Exchange:

production of a forward colorless system…

•P exchange Study of QCD

•Requires: – Accurate pleading measurement ( E <<0.10, small |t|) – Forward & Central measurement– large range for rapidity gap detection…

•Needs additional forward coverage for case of ATLAS…NO plans so far…

IP

p (ξ, t)

M2 = ξ sIP

Andrew Brandt – September 19 2003 Small-x 2003 – 13

Central (hard) DiffractionCentral (hard) Diffraction• Double Pomeron Exchange: production

of a central colorless bosonic system…Requires: – Accurate pleading measurement ( E <<0.10) – Central measurement, e.g. M = gg, H, …– Rapidity gap detection… Δη = lnξ

• Simulations by S. Tapprogge et al., (Helsinki Group, preprint HIP-2003/EXP)

• Predictions for ex(in)clusive production:– “Calibrated” with TeVatron data– Predictions for LHC vary – Many talks/discussions on DPE at this conference:

DPE is THE main argument (towards the Hi-PT community) for doing Forward Physics at LHC!

IP

IP

p (ξ1)

p (ξ2)

M2 = ξ1ξ2s

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Acceptance for Central Acceptance for Central ProductionProduction

• Combined acceptance of: All detectors- - - - 420 m + 215 m____ 215 m alone- - 420 m alone

• without 308 / 338 m location:

10-15 % loss in acceptance

J.Kalliopuska, J.Mäki, N.Marola, R.Orava, K.Österberg, M.Ottela, S.Tapprogge; Helsinki Group, preprint HIP-2003-11/EXP

IP

IP

p (ξ1)

p (ξ2)

M2 = ξ1ξ2s

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Resolution on Central MassResolution on Central Mass•Simple method:

Use estimate from most distant station first

•420 m•308 m•215 m

•~ 4% 1% (small large )

•Only exclusive process simulated

J.Kalliopuska, J.Mäki, N.Marola, R.Orava, K.Österberg, M.Ottela, S.Tapprogge; Helsinki Group, preprint HIP-2003-11/EXP

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Measurement of Central Measurement of Central DiffractionDiffraction

•requires TWO additional very small angle detector pairs at very large distance:– 308/338 m, and 420 m; i.e. in COLD part of LHC

•needs to break into LHC cryostats!•μStations?

– accuracy: O(10 μm), and edge-less– Hi-L running: rad-hard detectors

need VERY strong physics arguments to convince LHC(C)!

Andrew Brandt – September 19 2003 Small-x 2003 – 17

Summary - PlansSummary - Plans• Luminosity Baseline: CNI measurement + LUCID

– Coulomb normalization seems possible – intensive optics studies (with LHC/TOTEM – V. Avati) continue

– Development of Roman Pots and Detectors (with LHC/TOTEM – M. Oriunno)

• Luminosity Monitoring: LUCID well underway: • Other Monitors:

– Double photon muon pair process: simulation underway…– W/Z production monitors: needs detailed study…

• Forward Physics:– Detailed simulation study is very promising (Helsinki preprint)– presumes Roman Pots for ATLAS (as for CNI; and beyond 300

m??)– Initial trigger studies for 215 m (just enough time)

• Preparing a draft internal proposal (Fall ’03)• Next meeting at Orsay, Sept. 29th (Manchester in December)