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Forward Physics with the TOTEM CMS at the LHC Risto Orava. Forward physics at the LHC Signature studies Experimental layout An example: pp p+H+p Outlook. XIII ISVHECRI Pylos, Greece, 6-12 September 2004 R.Orava. - PowerPoint PPT Presentation
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Forward Physics with the TOTEMCMS at the LHC
Risto Orava
XIII ISVHECRI Pylos, Greece, 6-12 September 2004 R.OravaLow-x Workshop, Prague 17 September 2004 Risto Orava
• Forward physics at the LHC• Signature studies• Experimental layout• An example: ppp+H+p• Outlook
CMS/TOTEM
The Large Hadron Collider (LHC)
ATLAS
ALICE
LHC-B
LHC is built into 27 km the LEP tunnel
pp collisions at 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
Planned Startup on Spring 2007
Important part of the phase space is not covered by the generic designs at LHC. TOTEM CMS Covers more than any previous experiment at a hadron collider.
In the forward region (| > 5): few particles with large energies/small transverse momenta.
Charge flow
Energy flow
information value low: - bulk of the particles crated late in space-time
information value high: - leading particles created early in space-time
mic
rosta
tion a
t 19m
?
RPs
Total TOTEM/CMS acceptance (*=1540m)
TOTEM + CMS
lead
ing
pro
ton
s
lead
ing
pro
ton
s
Diffractive Scattering has distinctive signatures
Soft diffractive scattering
Hard diffractive scattering
Valence quarks in a bag with
r 0.1fm
Baryonic charge distribution
r 0.4fm
‘wee’ partons lns
Rapidity gapsurvival & ”underlying”event structures areintimately connectedwith a geometricalview of the scattering- eikonal approach!R.Orava
s-channel view
p
p
lns
lnMX2
jet
jet
Elastic soft SDE
hard SDE
hard CD
’Glansing’ scattering of proton fields
How to manage with the high-pT signatures in the environment of an underlying event?
Proton AntiProton
“Soft” Collision (no hard scattering)
Proton AntiProton
“Hard” Scattering
PT(hard)
Outgoing Parton
Outgoing Parton
Underlying Event Underlying Event
Initial-State Radiation
Final-State Radiation
Proton AntiProton
“Underlying Event”
Beam-Beam Remnants Beam-Beam Remnants
Initial-State Radiation
Unavoidable background to be removed from the jets before comparing to NLO QCD predictions
LHC: most of collisions are “soft’’, outgoing particles roughly in the same direction as the initial protons.
Occasional “hard’’ interaction results in large transverse momentum outgoing partons.
The “Underlying Event’’ is everything but the two outgoing Jets, including :
initial/final gluon radiation beam-beam remnants secondary semi-hard interactions
Min-Min-BiasBiasMin-Bias
How do we control the kinematics (DIS vs. hh)?
L dt = 1033 & 1037 cm2
Pomeron exchange (~exp Bt)
diffractive structure
pQCD
Photon - Pomeron interference
(* = 1540 m & 18 m)
d/
dt
(mb
/GeV
2)
Studying elastic scattering an soft diffraction requires special LHC optics. These will yield large statistics.
high-t
Diffractive Cross Sections are Large
0.375
Rel = el(s)/tot(s) Rdiff = [el(s) + SD(s) + DD(s)]/tot(s)
0.30
el 30% of tot at the LHC ? SD + DD 10% of tot (= 100-150mb) at the LHC ?
Inelastic rates are uncertain in the forward region
Event selection:• trigger from T1 or T2 (double arm o single arm)• Vertex reconstruction (to eliminate beam-gas bkg.)
Extrapolation for diffractive events needed
Lost events
Acceptance
simulated
extrapolated
detectedLoss at low masses
TOTEM will measure tot to 1%
TOTEM
Additional forward coverage opens up new complementary physics program at the LHC
• Investigate QCD: tot, elastic scattering, soft & hard diffraction, multi- rapidity gap events (see: Hera, Tevatron, RHIC...) - confinement.– Studies with pure gluon jets: gg/qq… - LHC as a gluon factory!
– Gluon density at small xBj (10-6 – 10-7) – “hot spots” of glue in vacuum?
– Gap survival dynamics, proton parton configurations (pp3jets+p) – underlying event structures
– Diffractive structure: Production of jets, W, J/, b, t, hard photons,– Parton saturation, BFKL dynamics, proton structure, multi-parton
scattering• Search for signals of new physics based on forward protons + rapidity gaps
Threshold scan for JPC = 0++ states in: pp p+X+p – spin-parity of X! (LHC as the e+e- linear collider in -mode.)
• Extension of the ‘standard’ physics reach of the CMS experiment into the forward region
• Luminosity measurement with L/L 5 %
0 0c bχ , χ
As a Gluon Factory LHC could deliver...
• О(100k) high purity (q/g = 1/3000) gluon jets with ET > 50 GeV in 1 year; gg-events as “Pomeron-Pomeron” luminosity monitor
• Possible new resonant states, e.g. Higgs (О(100) H bb events per year with mH = 120 GeV, L=1034)*, glueballs, quarkonia 0++ (b ), gluinoballs - complementary to inclusive analyses (bb, WW & decays)
• Invisible decay modes of Higgs (and SUSY)?!• CP-odd Higgs
• Squark & gluino thresholds well separated - practically background free signature: multi-jets & ET
- model independence (missing mass!) [expect O(10) events for gluino/squark masses of 250 GeV]
- an interesting scenario: gluino as the LSP with mass window 25-35 GeV(S.Raby)
• O(10) events with isolated high mass pairs, extra dimensions
gg
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
100
101
102
103
104
105
106
107
108
109
fixedtarget
HERA
x1,2
= (M/1.96 TeV) exp(y)Q = M
Tevatron parton kinematics
M = 10 GeV
M = 100 GeV
M = 1 TeV
422 04y =
Q2
(GeV
2 )
x
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
100
101
102
103
104
105
106
107
108
109
fixedtarget
HERA
x1,2
= (M/14 TeV) exp(y)Q = M
LHC parton kinematics
M = 10 GeV
M = 100 GeV
M = 1 TeV
M = 10 TeV
66y = 40 224Q
2 (G
eV2 )
x
longer Q2
extrapolation
smaller x
J. Stirling
Low-x Physics at the LHCGain in x-reach & Q2-range
In addition: The signatures of new physics have to be normalized: The Luminosity Measurement
Luminosity relates the cross section of a given process by:L = N/
A process with well known, calculable and large (monitoring!) with a well defined signature? Need complementarity.
Measure simultaneously elastic (Nel) & inelastic rates (Ninel), extrapolate d/dt 0, assume -parameter to be known:
(1+2) (Nel + Ninel)2
16dNel/dt|t=0
L =
Ninel = ? Need a hermetic detector.
dNel/dtt=0 = ? Minimal extrapolation to t0: tmin 0.01
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)
Forward Physics ScenariosProton
* (m)
rapiditygap L(cm-2s-1)
jetinelasticactivity
,e,, , ++,...
elastic scattering
total cross section
soft diffraction
hard diffraction
1540 18
1540
1540200-400
200-400 0.5
low-x physics
exotics (DCC,...)
DPE Higgs, SUSY,...central pair
central & fwd
inelasticacceptance gap survival
jetacceptance di-jet backgr
b-tag, ,J/,...
1028 -1032
1029 -1031
1028 -1033
1031 -1033
1031 -1033
TOTEM& CMS
TOTEM& CMS
TOTEM& CMS
central& fwd jets
di-leptonsjet-
mini-jetsresolved?
± vs. o
multiplicity
leptons’s
jetanomalies?
W, Z, J/,...
, K±,,...
0.5
1031 -1033
1031 -1033
200-400 0.5
200-400 0.5
mini-jets?
R.Orava
beam halo?
trigger
Correlation with the CMS Signatures
• e, , , , and b-jets:• tracking: || < 2.5• calorimetry with fine granularity: || < 2.5• muon: || < 2.5
• Jets, ETmiss
• calorimetry extension: || < 5
• High pT Objects• Higgs, SUSY,...
• Precision physics (cross sections...)• energy scale: e & 0.1%, jets 1% • absolute luminosity vs. parton-parton luminosity via
”well known” processes such as W/Z production?
R.Orava
• Leading Protons
• Extended Coverage of Inelastic Activity
• CMS
To Reach the Forward Physics Goals We Need:
Need to Measure Inelastic Activity and Leading Protons over Extended Acceptance in , , and –t. Measurement stations (Roman Pots) at locations optimized vs. the LHC beam optics. Both sides of the IP.
147 m147 m 180 m180 m 220 m220 m
LP1LP1 LP2LP2 LP3LP3
Measure the deviation of the leading proton location from the nominal beam axis () and the angle between the two measurement locations (-t) within a doublet.Acceptance is limited by the distance of a detector to the beam.Resolution is limited by the transverse vx location (small ) and bybeam energy spread (large ).For Higgs, SUSY etc. heavier states need LP4,5 at 300-400m!
TOTEM ROMAN POT IN CERN TEST BEAM
Microstation – Next Generation Roman Pot
-station concept (Helsinki proposal)
Silicon pixel detectors in vacuum (shielded)
Movable detector
Very compactA solution for 19m, 380 & 420m?
• more than 90% of all diffractive protons are seen!
• proton momentum can be measured with a resolution of few 10-3
Diffraction at high *: AcceptanceLuminosity 1028-1030cm-2s-1 (few days or weeks)
~14 m
CMSCMS T1-CSC: 3.1 < < 4.7
T2-GEM: 5.3 < < 6.5
T3-MS: 7.0 < < 8.5 ?
10.5 mT1T1 T2T2
T3?T3?
CMS tracking is extended by forward telescopes on both sides of the IP
~19 m
- A microstation (T3) at 19m is an option.
CASTORCASTOR
Running Scenarios 1: High & Intemediate *
Scenario(goal)
1low |t| elastic,tot , min. bias
2diffr. phys.,
large pT phen.
3intermediate |
t|, hard diffract.
4large |t| elastic
* [m] 1540 1540 200 - 400 18
N of bunches 43 156 936 2808
Half crossing angle [rad]
0 0 100 - 200 160
Transv. norm. emitt. [m rad]
1 1 3.75 3.75 3.75
N of part. per bunch
0.3 x 1011 0.6 x 1011
1.15 x 1011
1.15 x 1011 1.15 x 1011
RMS beam size at IP [m]
454 454 880 317 - 448 95
RMS beam diverg. [rad]
0.29 0.29 0.57 1.6 - 1.1 5.28
Peak luminos. [cm-2 s-1]
1.6 x 1028 2.4 x 1029 (1 - 0.5) x 1031 3.6 x 1032
- low * physics will follow...
The process: pp p + H + p
p
p
b-jet
b-jet
p1
p2
p’
p”
b
b0
5
-5
10
-10
-
-0++
H
MH2 = (p1 + p2 – p’ – p”)2 12s (at the limit, where pT’ & pT” are small)
1 =p’q1/p1q1 1-p’/p1 2 = 1-p”q2/p2q2 1-p”/p2
0++
q1
q2
Leading proton studies at low *
GOAL: New particle states in Exclusive DPE
• L > few 10 32 cm2 s1 for cross sections of ~ fb (like Higgs)
• Measure both protons to reduce background from inclusive
• Measure jets in central detector to reduce gg background
Challenges:
• M 100 GeV need acceptance down to ’s of a few ‰
• Pile-up events tend to destroy rapidity gaps L < few 10 33 cm2 s1
• Pair of leading protons central mass resolution background
rejection
A study by the Helsinki group in TOTEM.
Central Diffraction produces two leading protons, two rapidity gaps and a central hadronic system. In the exclusive process, the background is suppressed and the central system has selected quantum numbers.
JPC = 0++ (2++, 4++,...)
Gap GapJet+Jet
min max
Survival of the rapidity gaps?1
1 V.A.Khoze,A.D.Martin and M.G.Ryskin, hep-ph/0007359R.Orava
Measure the parity P = (-1)J:d/d 1 + cos2
Mass resolution S/B-ratio
MX212s
The Experimental Signatures: pp p + X + p
b-jet
CMS
- Leading protons on both sides down to 1‰- Rapidity gaps on both sides – forward activity – for || > 5- Central activity in CMS
- resolution in ?-beam energy spread?
- vertex position in the transverse plane?
-
Aim at measuring the:
Detector Detector
p2’ p1’
b-jet_
Leading Proton Detection 147m 180m 220m0m 308m 338m 420 430m
IP
Q1-3
D1
D2 Q4 Q5 Q6 Q7 B8 Q8 B9 Q9 B10 B11Q10
Jerry & Risto
= 0.02
Mass Acceptance
Both protons are seen with 45 % efficiency at MX = 120 GeV
Some acceptance down to: MX = 60 GeV
308m & 420m locations select symmetric proton pairs acceptance decreases.
308 m420 m
pp p + X + p
MX (GeV)
MX = 60 GeV
MX = 120 GeV
All
45%
30%
15%
All detectors combined
308m
420m
Resolution improves with increasing momentum loss
Dominant effect: transverse vertex position (at small momentum loss) and beam energy spread (at large momentum loss, 420 m)/detector resolution (at large momentum loss, 215 m & 308/338 m)
proton momentum loss
proton momentum loss
Momentum loss resolution at 420 m
DPE Mass Measurement at 400m
Gaussian (M) vs. central massassuming xF/xF = 10-4
symmetric case:
Central Mass (GeV)
(M
) (G
eV
)
= (1.5 - 3.0) GeV (xF/xF = (1-2)10-
4)
65% of the data
20 GeV < MX < 160 GeV
(MXmax determined by the aperture of the last dipole,B11, MXmin by the minimum deflection = 5mm)
Helsinki group/J.Lamsa & R.O.
Note: (M)/M = 1.1% (M) = 1.3 GeV - Gaussian width- To contain 87% of the signal need 3x(M) = 3.9 GeV
SUMMARY:TOTEM opens up Forward Physics to the LHC
TOTEMCMS covers more phase space than any previous experiment at a hadron collider.
Fundamental precision measurements on elastic scattering, total cross section and QCD:• non-perturbative structure of proton• studies of pure gluon jets – LHC as a gluon factory• gluon densities at very small xBj…• parton configurations in proton
Searches for signals of new physics:• Threshold scan of 0++ states in exclusive central diffraction: Higgs, SUSY (mass resolution crucial for background rejection)
Extension of the ‘standard’ physics reach of CMS into the fwd region & Precise luminosity measurement