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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