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Forward Physics with CMS

Marek Taševský (Univ.Inst. Antwerp)DIS 04 - Štrbské Pleso 16/4 2004

IntroductionPhysics

Detectors options

Slides byAlbert De Roeck(CERN)

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The Large Hadron Collider (LHC) PP collisions at s = 14 TeV

5 experiments

25 ns bunch spacing 2835 bunches 1011 p/bunch

Design Luminosity:1033cm-2s-1 -1034cm-2s-1

100 fb-1/year

23 inelastic eventsper bunch crossing

TOTEM

In LEP tunnel(circonf. 26.7 km)

Planned Startup: April 1st 2007

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The CMS experimento Tracking

o Silicon pixelso Silicon strips

o Calorimeterso PbW04 crystals for Electro-magn.o Scintillator/steel for hadronic part

o 4T solenoido Instrumented iron for muon detection

o CoverageoTracking 0 < || < 2.5-3o Calorimetry 0 < || < 5

A Huge enterprise !

Main program: EWSB, Beyond SM physics…

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Diffraction and Forward PhysicsTOTEM: • TDR submitted in January 2004/ in the process of approval• TOTEM stand alone

– Elastic scattering, Total pp cross section and soft diffraction. Totem has no central detector

• TOTEM together with CMS:– Full diffractive program with central activity. TOTEM will be included as a

subdetector in CMS (trigger/data stream)CMS:• EOI submitted in January 2004:

– Diffractive and low-x physics part of CMS physics program– Diffraction with TOTEM Roman Pots and/or rapidity gaps

• LOI in preparation for new forward detectors (CASTOR, ZDC)– Additional options being studied

ATLAS:• LOI submitted (March) for RP detectors to measure elastic scattering/ total

cross sections/luminosity. Diffraction will be looked at laterALICE, LHCb: no direct forward projects plans but keeping eyes open.

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The TOTEM Experiment

TOTEM physics program: total pp, elastic & diffractive cross sectionsApparatus: Inelastic Detectors & Roman Pots (3 stations)

CMSIP

147 m 215 m

-t=10-1

-t=10-2

High * (1540m): Lumi 1028-1031cm-2s-1 (few days or weeks) >90% of all diffractive protons are seen in the Roman Pots. Proton momentum measured with a resolution ~10-3

Low *: (0.5m): Lumi 1033-1034cm-2s-1 215m: 0.02 < < 0.2 300/400m: 0.002 < < 0.2 (RPs in the cold region)

180 m

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TOTEM/CMS forward detectors

T1

T2

TOTEM T2

CASTOR 9,71 λI

T2

T1/T2 inelastic event taggers T1 CSC/RPC tracker (99 LOI) T2 GEM or Silicon tracker (TOTEM/New) CASTOR Calorimeter (CMS/New)

T1 3< <5T2 5< <6.5

5.3 << 6.7

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CMS/TOTEM Study

• Common working group to study diffraction and forward physics at full LHC luminosity approved by CMS and TOTEM (spring 2002)

(ADR/ K. Eggert organizing so far) Use synergy for e.g. simulation, physics studies & forward detector

option studies.

• Common DAQ/Trigger for CMS & TOTEM• Discussions on T2• Common simulation etc…• Share physics studies

Common LOI on diffractive physics (pending LHCC approval) on the time scale of ~1 year

CMS/TOTEM is the largest acceptance detector ever built at a hadron collider

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For the first time at a collider large acceptance detector which measures the forward energy flow

1 day run at large beta (1540m) and L=1029cm-2s-1: 100 million minimum bias events, including all diffractive processes

>90% of all diffractive protons are detected

mic

rosta

tion a

t 19m

?

RPs

Total TOTEM/CMS acceptance (*=1540m)

CMS/TOTEM is the largest acceptance detector ever built at a hadron collider

TOTEM+CMS

T1,T2 T1,T2

Ro

ma

n P

ots

Ro

ma

n P

ots

Charged particles

Energy flux

CMS/TOTEM Study

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Forward Physics Program• Soft & Hard diffraction

– Total cross section and elastic scattering– Gap survival dynamics, multi-gap events, proton light cone (pp3jets+p)– Diffractive structure: Production of jets, W, J/, b, t, hard photons– Double Pomeron exchange events as a gluon factory (anomalous W,Z production?)– Diffractive Higgs production, (diffractive Radion production?)– SUSY & other (low mass) exotics & exclusive processes

• Low-x Dynamics– Parton saturation, BFKL/CCFM dynamics, proton structure, multi-parton

scattering…• New Forward Physics phenomena

– New phenomena such as DCCs, incoherent pion emission, Centauro’s• Strong interest from cosmic rays community

– Forward energy and particle flows/minimum bias event structure• Two-photon interactions and peripheral collisions• Forward physics in pA and AA collisions• Use QED processes to determine the luminosity to 1% (ppppee, pppp)

Many of these studies can be done best with L ~1033 (or lower)

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Diffraction at LHC:• PP scattering at highest energy • Soft & Hard Diffraction

< 0.1 O(1) TeV “Pomeron beams“ E.g. Structure of the Pomeron F(,Q2) down to ~ 10-3 & Q2 ~104 GeV2

Diffraction dynamics? Exclusive final states ? • Gap dynamics in pp presently not fully understood!

proton momentumlossmeasured in RPs

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DPE: from Di-jet events• Et> 100 GeV/2 figsPt>100 GeV/c for different Pomeron structure functions

H1 fit 6

H1 fit 5

H1 fit 4(x 100)

(1-x)5

x(1-x)

H1 fit 6

d (pb) events

High region probed/ clear differences between different Pomeron SFs

=jets ET e-/(s ) ; from Roman Pots; ET and from CMS

(using POMWIG generator)

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Hgap gap

b

b -jet

-jet

Diffractive Higgs ProductionExclusive diffractive Higgs production pp p H p : 3-10 fbInclusive diffractive Higgs production pp p+X+H+Y+p : 50-200 fb

p p

beam

p’

p’roman pots roman pots

dipole

dipole

~New: Under study by many groups

22 )''( ppppM H

Advantages Exclusive: Jz=0 suppression of ggbb background Mass measurement via missing mass

E.g. V. Khoze et alM. Boonekamp et al.B. Cox et al. …

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MSSM Higgs

Kaidalov et al.,hep-ph/0307064

100 fb

1fb

SM Higgs: (30fb-1)11 signal eventsO(10) background events

Cross section factor~ 10 larger in MSSM(high tan)

Also:Study correlations between the outgoingprotons to analyse the spin-parity structure ofthe produced boson 120 140

See talk of A. Martin

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Beyond Standard Model

Diffractive production of new heavy states pp p + M + pParticularly if produced in gluon gluon (or ) fusion processes

Examples:Light CP violating Higgs Boson MH < 70 GeV B. Cox et al.

Light MSSM Higgs hbb at large tan Light H,A (M<150 GeV) in MSSM with large tan (~ 30) S/B > 10 Medium H,A (M=150-200 GeV) medium tan ?V. Khoze et al. Radion production - couples strongly to gluons Ryutin, Petrov

Exclusive gluino-gluino production?Only possible if gluino is light (< 200-250 GeV) V. Khoze et al.

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SM Higgs Studies Needs Roman Pots at new positions 320 and/or 420 mTechnical challenge: “cold” region of the machine, Trigger signals…

Curves:HelsinkiGroup

Dots:Fast sim.usingDPEHIGGSMC model

Mass of Higgs

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Diffractive Higgs Production

Mass resolution vs. central massfrom protons measured in roman potsassuming xF/xF = 10-4

Exclusive channel pp p H p advantagesGood mass resolution thanks to missing massmethod:M = O(1.0 - 2.0) GeV (including systematics)

Study possible in the b-quark decay modeb-quark background suppression: (JZ =0 states)!!Switch of dominant background (at LO)!

Inclusive production pp p+X+H+Y+p :100 x larger cross section but background notsuppressed (gain under study) and missing massless effective

Mass r

esolu

tion

(G

eV

)

Central Mass (GeV)

symmetric case:

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Detectors at 300m/400m

Detectors in this region requires changes in the machine

• Physics Case– Can we expect to see a good signal over background? Signal understood (cross section) ? Needs good understanding of the background (inclusive!) Needs more complete simulations (resolutions, etc.)

• Trigger– 300m/400m signals of RPs arrive too late for the trigger Can we trigger with the central detector only for L1? Note: L1 2-jet thresholds ET > ~150 GeV

• Machine– Can detectors (RPs or microstations) be integrated with the

machine? Technically there is place available at 330 and 420 m

Of interest for both ATLAS and CMS

Some Major Concerns:

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Low-x at the LHC LHC: due to the high energy can reach small values of Bjorken-

x in structure of the proton F(x,Q2)Processes: Drell-Yan Prompt photon production Jet production W production

If rapidities above 5 and masses below 10 GeV can becovered x down to 10-6-10-7

Possible with T2 upgrade in TOTEM(calorimeter, tracker) 5<< 6.7 !

Proton structure at low-x !!Parton saturation effects?

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Low-x at the LHC

Rapidity ranges of jets or leptons vs x range

||<5 5<||<7

7<||<9 5.5<||<7.8KimberMartinRyskin

Log10(x)

Log10(x) Log10(x)

Log10(x)

Shadowing corrections fordifferent saturation radii R

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Di-jets in pp scattering

jet

jet

Azimuthal decorrelation betweenthe 2 jets versus rapidity distancebetween the 2 jets

Large range needed Rise?

Measurements for low-x (BFKL) dynamics

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High Energy Cosmic Rays

Interpreting cosmic ray data dependson hadronic simulation programsForward region poorly known/constrainedModels differ by factor 2 or moreNeed forward particle/energy measurements e.g. dE/d…

Cosmic rayshowers:Dynamics of thehigh energy particle spectrumis crucial

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Relative luminosity S = L/Lpp:: ~ 0.1% for W> 200 GeVMust tag protons at small |t| with good resolution: TOTEM Roman Pots!

Process

WWA spectrum

Reach highW values!!

Two-photon interactions at the LHC

pp

CMS Totem

K. Piotrzkowski

Double tags

All events

Elastic events

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Two-photon interactions at the LHC

pp

October 2001 K.Piotrzkowski, Erice Workshop

Physics Menu - Highlights

H0

pb (at W=MH=200 GeV)

pb

tt

pb

nb

All ?

W+W-

+ SUSY processes

New studies: p interactions with 10-100x Luminosity

Sensitivity to LargeExtra Dimensions

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SM HIGGS caseNumber of Higgs events for single tags and assuming integrated lumi-nosity of 30, 0.3 and 0.03 fb-1 for pp, pAr and ArAr collisions, respectively.

Significant production rates and very clean signatures available - both transverse and longitudinal missing energyExclusive production!

Range up to 200-250 GeV

for single tags

SUSY K. Piotrzkowski

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Status of the Project

• Common working group to study diffraction and forward physics at full LHC luminosity approved by CMS and TOTEM (spring 2002)

(ADR/ K. Eggert organizing) Use synergy for e.g. simulation, physics studies & forward detector

option studies. Some of this happened e.g. RP & T2 simulation, detector options

• Detector options being explored– Roman Pot/microstations for beampipe detectors at 150, 215 , add 310 & 420 m ? (cold section!)– Inelastic detectors T1 CSC trackers of TOTEM (not usable at CMS lumi) Replace T2 with a compact silicon tracker (~ CMS technology) or

GEMs Add EM/HAD calorimeter (CASTOR) behind T2 Add Zero degree calorimeter (ZDC) at 140 m

• Common DAQ/Trigger for CMS & TOTEM• Common simulation etc…

13570

Tungsten and quartz platesLength 152 cm~ 9I

Electromagnetic section8 sectors/ needs extension

APD detectors

A calorimeter in the range 5.3 << 6.7 (CASTOR)

A Forward Calorimeter (CMS)

T2 CASTOR

Position of T2 and Castor (7/2/03)

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Beam pipe splits 140m from IR

ZDC LOCATION

BEAMS

“Spectators”

ZDCZDC

ZDCZDC

Tungsten/ quartz fibre or PPAC calorimeterEM and HAD section

Funding pending in DOE

ZDC: zero degree calorimeter

M. Murray

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Opportunities for present/new Collaborators

• CMS central detector– Diffractive Gap Trigger (possible in CMS trigger but needs to be

studied)• T2 region

– Calorimeter (CASTOR)• Add granularity (silicon, PPAC,…)• Castor trigger• So far only one side of CMS equipped (500 kCHF)

– T2 tracker (part of TOTEM, but still in flux…)• May need participation from CMS (if silicon option)• May need new tracker by CMS (if GEM option)… watch TOTEM TDR

• Detectors at 300/400m – Completely new project– Needs new resources (there are interested parties in CMS & ATLAS)

• ZDC small project but funding not yet garanteed• New detectors in the range 7< <9??? (20 m from IP)

Certainly help welcome on simulation tools, detailed physics studies…

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Rapidity Gaps at LHC

Number of overlap events per bunch crossing versus LHC lumi

distribution of nr. of int. per bunch crossing

103

4

10331032

1.1033 2.1033`

1 int. in 22% 1 int. in 4%

Doable at startup luminosity without Roman Pots!

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Summary• A study group has been formed to explore the common use of CMS

and TOTEM detectors and study the forward region. – Physics Interest

- Hard (& soft) diffraction, QCD and EWSB (Higgs), New Physics - Low-x dynamics and proton structure - Two-photon physics: QCD and New Physics - Special exotics (centauro’s, DCC’s in the forward region) - Cosmic Rays, Luminosity measurement, (pA, AA…)

– Probably initial run at high * (few days/weeks 0.1-1 pb-1 )– Runs at low * (10-100 fb-1 )

• NEW: CMS officially supports forward physics as a project!– Expression of interest for the LHCC– Opportunities for present/new collaborators to join complete forward detectors for initial LHC lumi However: Contribution to LOI needed NOW