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V.AvatiPhysics at LHC
TOTEM and Diffractive Physics at the LHC
INFN Sezione di Bari and Politecnico di Bari, Bari, Italy Case Western Reserve University, Cleveland, Ohio,USA
CERN, Geneva, Switzerland
Estonian Academy of Sciences, Tallinn, Estonia
Università di Genova and Sezione INFN, Genova, Italy
Università di Siena and Sezione INFN-Pisa, Italy University of Helsinki and HIP, Helsinki, FinlandAcademy of Sciences, Praha, Czech RepublicWarsaw University of Technology, Plock,Poland Penn State University, University Park, USABrunel University, Uxbridge, UK
V. Avati
on behalf of the
TOTEM Collaboration
Physics at LHC
Krakow, 2-8 July 2006
V.AvatiPhysics at LHC
Physics programPhysics program
Total cross-section with a precision of 1%Total cross-section with a precision of 1%
Elastic pp scattering in the range 10 Elastic pp scattering in the range 10 -3-3 < t = (p < t = (p))22 < 10 GeV < 10 GeV22
Soft diffractionSoft diffraction
Measurement of leading particlesMeasurement of leading particles
Particle and energy flow in the forward directionParticle and energy flow in the forward direction
Soft and hard diffraction in Single and Double Pomeron ExchangeSoft and hard diffraction in Single and Double Pomeron Exchangeproduction of jets, W, heavy flavours.....production of jets, W, heavy flavours.....
Central Exclusive particle production Central Exclusive particle production
Low-x physicsLow-x physics
and and p physicsp physics
WWIITTHH
CCM M S S
V.AvatiPhysics at LHC
COMPETE Collaboration:
pp Total Cross-Sectionpp Total Cross-Section
Current models predict for
14 TeV: 90 – 130 mb
Aim of TOTEM: ~ 1% accuracy
Luminosity independent method:
COMPETE Collaboration fits all available hadronic data
and predicts at LHC:
PRL 89 201801 (2002)]
V.AvatiPhysics at LHC
Experimental apparatusExperimental apparatus
V.AvatiPhysics at LHC
• 5 planes with measurement of three coordinates per plane.
• 3 degrees rotation and overlap between adjacent planes
• Primary vertex reconstruction• Trigger with wires
3.1< || <4.7
~3 m1 arm
T1 TelescopeT1 Telescope
V.AvatiPhysics at LHC
V.AvatiPhysics at LHC
5.3<|| < 6.5
GEM (Gas Electron Multiplier)
10 half-planes @ 13.5m from IP5
40 cm
T2 TelescopeT2 Telescope
CASTOR Calorimeter(CMS)
Full Telescope Mock up
V.AvatiPhysics at LHC
256 (width: 80 m,pitch: 400 m) strips
1536 pads 54() x 22() 2x2 - 7x7 mm2
x= 0.06 x 0.017L1 Trigger
pads
stripsRead-out board
V.AvatiPhysics at LHC
Roman Pot unit:- Measurement of very small p scattering angles (few rad)- Vertical and horizontal pots mounted as close as possible- BPM fixed to the structure gives precise position of the beam- TOTEM at the RP: beam ≈ 80 m- Leading proton detection at distances down to 10 beam + d- Need “edgeless” detectors that are efficient up to the physical edge to minimize “d”
reconstructed track
Roman PotRoman Pot
4 m
10 planesSi edgeless det.
SPS Test Beam '04
V.AvatiPhysics at LHC
Lateral Pot Vertical Pots BPM
V.AvatiPhysics at LHC
TOTEM ROMAN POT IN CERN SPS BEAM
V.AvatiPhysics at LHC
Detector’s ID50
m
66 μm pitch
dead
are
a
Pitch adapter on detector
Si Edgeless Detectors for RPSi Edgeless Detectors for RP
Planar technology with CTS(Current Terminating
Structure)
Test Beam 2003
2006 production
I2I1
+-
biasing ring Al
p+
n+
cut edge
current terminating
ring
Al
SiO2
n-type bulkp+
50m
AC coupled microstrips made in planar technology with
specific guard-ring design and biasing scheme. Full production by the end of 2007
First measurement of leakage current at CERN:
60 nA at 200 V (excellent)
Strong improvements on the cut at the sensitive edge
Also available another technology: 3D/planar edgeless Si-det.
V.AvatiPhysics at LHC
Totem OpticsTotem Optics TOTEM needs special/independent short runs at high-high-* * and and low low for precise for precise measurement of the measurement of the scattering angles of a few few radrad
As consequence of high * : large beam size at IP *= √* ~ 0.3 rad
√* ~ 0.4 mm
Require parallel-to-point focusing: trajectories of proton scattered at the same angle but at different vertex locations ( y~
y)
Reduced number of bunches (43, 156) to avoid interactions further downstream
Baseline optics *=1540 m: Parallel-to-point focusing in both transverse planes, allows
very low-t detection (-t ~ 2 10-3 GeV2)
requires special injection optics
probably not available at beginning of LHC
Investigation on *=90 m : paralle-to-point focusing only in vertical plane
t detection down to ~ 2 10-2 GeV2
achievable by un-squeezing the standard LHC injection optics
V.AvatiPhysics at LHC
1.15 (0.6 - 1.15) 1.150.3 N of part. per bunch
(x 1011)
2 x 1030
2.3
200
3.75
0
156
90
Soft &
semi-hard diffraction
2.4 x 1029
0.29 - 0.57
454 - 880
1 - 3.75
0
156
1540
Soft diffraction
3.6 x 10321.6 (7.3) x 1028Peak luminosity
[cm-2 s-1]
5.280.29 (2.3)RMS beam diverg.
[rad]
95454 (200)RMS beam size at IP [m]
3.751 (3.75)Transv. norm. emitt. [m rad]
1600Half crossing angle
[rad]
280843N of bunches
18, 2, 0.51540 (90)
large |t| elasticlow |t| elastic,
tot ,
min bias
Physics:
*[m]
Running ScenarioRunning Scenario
V.AvatiPhysics at LHC
Elastic ScatteringElastic Scattering
Good acceptance for high-t values Parallel-to-point focusing
*=1540
*=2*=90
Log(-t) GeV2Log(-t) GeV2
V.AvatiPhysics at LHC
Elastic ScatteringElastic Scattering
Detector distance to the beam: 1.3 mm (*=1540) 6 mm (*=90)
*=1540
*=2*=90
Log(-t) GeV2Log(-t) GeV2
V.AvatiPhysics at LHC
Elastic scattering: resolutionElastic scattering: resolution
resolution: test collinearity of particles in the 2 arms -> background reduction
1540m
1o
V.AvatiPhysics at LHC
Extrapolation of Elastic Cross Section to t=0Extrapolation of Elastic Cross Section to t=0
0.1 %0.2 radAngular spread
0.08 %20 mBeam -- detector alignment
0.1 %0.05 %Beam energy uncertainty
0.07 %107 eventsResolution, statistics (10h@1028):
Uncertainty inExtrapolation
Effect(=1540 m)
Theoretical models indetermination:
=1540 m < 0.1%=90 m ~ 0.5%
At =90 m some systematcs effects should be less important....
Total < 0.5 %
V.AvatiPhysics at LHC
Inelastic Cross SectionInelastic Cross Section
The inelastic telescopes T1/T2:The inelastic telescopes T1/T2:
provide full inclusive trigger
reconstruct the primary vertex to discriminatebeam-gas and beam-beam interaction
Trigger efficiency:Trigger efficiency:
NSD : >99% SD: 82%
Extrapolation of SD cross section to large 1/M2 using d/dM2 ~ 1/M2
V.AvatiPhysics at LHC
Total cross sectionTotal cross section
0.10.1----3030Elastic Elastic ScatteringScattering
0.020.02----11Double Double PomeronPomeron
0.10.10.30.32.82.877Double Double diffractivediffractive
0.60.62.52.5--14142 x single 2 x single diffractivediffractive
0.060.060.060.060.30.35858Minimum Minimum biasbias
Uncertainty Uncertainty after after
extrapolationextrapolation
Single Single armarm
DoubleDouble
armarm
Trigger Losses (mb)
tot/tot ~ 1 % (few % =90m) work in progress....
V.AvatiPhysics at LHC
Elastic Scattering Cross SectionElastic Scattering Cross Section =90 =2
2E9 -
1.5E6 1E6
4E3 1.2E5
5E2 4E4
30 3E3
1 160
0.3 50
0.3pb-1 10 pb-1 ∫Ldt
Num
ber o
f even
ts (BSW
model) 2
20m
V.AvatiPhysics at LHC
Diffractive protonsDiffractive protons
=1540
=2,0.5
Log
p/
pLog(-t) (GeV2)
=90
=1540
=90
=2,0.5
Log(M) (GeV)
diffr. protons detected 1-arm 2-armdiffr. protons detected 1-arm 2-arm (incl. SD) (incl. DPE)(incl. SD) (incl. DPE) ~50% ~30% ~50% ~30% ~90% ~80% ~90% ~80%
V.AvatiPhysics at LHC
50%
Central Mass resolution (from protons)Central Mass resolution (from protons)
30%=1540 m =90 m
Sample of DPE events M=√12s
CMS/TOTEM common physics program
The combined coverage of CMS/Totem makes it possible to study a wide range of physics subjects in diffractive interactions – from QCD and the low-x structure of the proton, to the production of SM and MSSM Higgs.
A document describing the program is foreseen in autumn
Wide coverage in pseudorapidity + Proton(s) detection
RP 220m
FP420
=1540
=2,0.5
=90Lo
g
p/p
TOTEM CMS TOTEM
NB: Don’t be scared by the old nomenclature – diffraction, Pomeron… All of this now understood in terms of quarks, gluons and QCD
Single Diffraction
Double Pomeron Exchange
X
X
Processes characterized by 2 gluon exchange withvacuum quantum numbers (“Pomeron”)
Large Rapidity Gap(s) between the proton(s) and X
X measured by central detectors
Scattered proton(s) may be measured by Roman Pots
X=anything : dominated by soft physics SD and DPE inclusive cross sections, their s, t, MX
dependences are fundamental parameters of non-perturbative QCD. Must be measured at LHC !
X includes jets, W’s, Z’s, Higgs (!): hard processes calculable in pQCD Give info on proton structure (dPDFs and GPDs), QCD at high parton densities, multi-parton interactions etc, discovery physics some of this can only be obtained in diffractive interactions
Physics Motivation
Running scenario
pp->pX pp->pjjX pp->pjj (vector bosons pp->pXp pp->pjjXp pp->pjjp heavy quarks,Higgs...)
soft diffraction (semi)-hard diffraction hard diffraction
Cross section Luminosity
m1540 90 2 0.5
L (cm-2 s-1) 1029 1030 1032 1034
TOTEM runs Standard runs
The accessible physics is a function of the luminosity and *
Low Luminosity (<10Low Luminosity (<103232 cm cm-2-2ss-1-1): low and high ): low and high ** Measure inclusive SD and DPE
cross sections and t, MX dependence Rapidity Gap selection Forward Drell-Yan Validation of Cosmic Ray generators
High Luminosity (> 10High Luminosity (> 103232 cm cm-2-2ss-1-1) : low) : low** (routine CMS data taking)
Measure SD and DPE in presence of hard scale (dijets, vector bosons, heavy quarks): dPDF, GPD
• and p phyics
> 10> 103333 cm cm-2-2ss-1-1
Discover the SM or MSSM Higgs in central exclusive production
Physics menu
Running with TOTEM optics: large Running with TOTEM optics: large proton acceptanceproton acceptance
No pile-upNo pile-up
Pile-up not negligible:Pile-up not negligible:main source of backgroundmain source of background
Need additional forward protonNeed additional forward protondetectordetector
Example for Central Exclusive Production: H(120)->b bbar
2-jets (ET>40GeV) & single-arm RP 220m
Trigger Studies (low *) Trigger is an important limiting factor to select diffractive events (“low” pT processes)
CMS trigger bandwith limits: L1 : O(1) kHz ; HLT : O (1) Hz
Combinations of TOTEM RP with the standard CMS trigger conditions (jets, muons) : it is possible tolower the jet/muon thresholds substantially and stay in the limits
The CMS trigger menus now foresee 1% of the trigger bandwidth 12%on L1 and HLT for a dedicated diffractive trigger stream
M. Grothe et al., proceedings HERA-LHC workshop '05,and CMS Note 2006/054 & TOTEM Note 2006/01
Low luminosity: soft DPE & SD
Trigger (special optics): DPE : 2 proton trigger (anti collinearity condition) +T1/T2SD : 1 p + T1/T2 opposite
Measure cross sections, t, M dependence
Measure the central Mass via: proton(s)rap-gap relation calorimeters
• Transition from soft to semi-hard scale: in the soft sample, “contamination” of (low pT)-dijets events
=90 m in 0.3pb-1
~10M events of inclusive DPE/SD ~1K events of DPE-dijets (low pT) ~10K events of SD-dijets “
GAP (T1/T2/Calorimeter) vs ln()
Limit of direct measurement
Inclusive DPE and SD production of B mesons
pp -> B+X p (p) J/psi -> Event yields in 10 fb-1 : DPE ~ 10 SD ~ 2K
Background and pile-up effect under study
Muon trigger thresholds one limiting factor in event yield
Inclusive SD and DPE ttbar production pp->p+X+(tt)+X+p tt->bbqqttbar in semileptonic decay channel
Event yield in 10 fb-1
DPE ~ 1-100 depending on theoretical modelSD ~ 30 times larger cross-section
Heavy flavour diffractive production
Di-muon mass, signal+back., SD
Light SM/MSSM Higgs in central exclusive production
shields color chargeof other 2 gluons
Vacuum quantumnumbers “DoublePomeron Exchange”
pp->pHp
Extensive study of theoretical models & MC generators
H->bbar MH=120 GeV only few events expected in 30fb-1 and S/B ~ 0.1-1
H->WW MH>130 GeV Nev~3-6 for 30 fb-1
Background and pile-up studies in progress
Cross-section is expected to be orders of magnitude higher in MSSM model for high tan
(M)/M
4%
1.5%
Cosmic rays connection
Interpreting cosmic ray data depends on hadronic simulation programs Forward region poorly known/constrained Models differ up to a factor 2 or more
Need forward particle/energy measurements: LHC center-of-mass energy corresponds to Elab=1017 eV
Achievable at low luminosity
T1/T2/Castor
Summary
TOTEM will be ready for data-taking at the LHC start:
Measure total pp cross-section (and luminosity) with a precision of 1 % with * = 1540 m
(Possible early measurement with *=90 m)
Measure elastic scattering in the range 10-3< t < 10 GeV 2
In collaboration with CMS:
soft diffractionsemi-hard diffraction (pT > 10 GeV)
hard diffractionExclusive Double Pomeron Exchange
Studies of forward particle production
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