p. 1Mario Deile –
DIS 2004DIS 2004
Mario Deile
CERN
on behalf of the TOTEM Collaboration
16.04.2004
TOTEM: Forward Physics at the LHC
p. 2Mario Deile –
• Elastic p-p scattering cross-section d/dt in the range 10-3 GeV2 < –t < 10 GeV2
• Total p-p cross section at 14 TeV with 1% uncertainty using the Optical Theorem (luminosity independent method)
• Diffractive events (together with CMS).• Absolute luminosity measurement and calibration of
CMS luminosity monitors
Physics Objectives of TOTEM
p. 3Mario Deile –
Detector Configuration
~14 m
CMSCMS T1:3.1 << 4.7
T2: 5.3 < < 6.5
10.5 m T1T1 T2T2
RP1RP1 RP2RP2 RP3RP3
220 m220 m180 m180 m147 m147 m
p. 4Mario Deile –
~ 90 % of all diffractive protons are detected
mic
rosta
tion a
t 19m
? RPs
Total TOTEM/CMS acceptance (*=1540m)
CMS+TOTEM: largest acceptance detector ever built at a hadron collider
Ro
ma
n P
ots
TOTEM+CMS
T1,T2 T1,T2
Ro
ma
n P
ots
Charged particles
Energyflux
CMS + TOTEM: AcceptancedNdN
chch/d/d
dE
/ddE
/d
p. 5Mario Deile –
T1 Telescope: Cathode Strip Chambers
• Two telescopes (forward and backward)• 5 planes of cathode strip chambers (CSC)• coverage = 2 • 3.1 < || < 4.7. • 3° rotation from plane to plane to improve pattern recognition
~3m
0.8 1.1 m• 3 projections measured
• ~350 cathode strips / detector, 5 mm pitch;
analogue read-out (CMS Buckeye chip);
resolution: x ~ 0.5 mm, y~ 0.9 mm
• ~210 anode wires / det., ( 30 m, 3 mm pitch);
digital read-out (CMS AD16 chip) provides trigger
p. 6Mario Deile –
Castor Calorimeter (CMS)
Vacuum Chamber
1800 mm400 mm
T2 Telescope: Gas Electron Multiplier
T2 GEM Telescope:• 8 planes• 5.3< ll < 6.7• 13.5 m from IP• COMPASS technology
Pads (trigger):digital readout via VFAT x = 0.06 x 0.017 2x2 mm2 7x7 mm2
Equidistant strips: analogue readout via APV2580 m wide, 400 m pitch
p. 7Mario Deile –
Proton Detectors: Roman Pots
Beampipes
Measurement of very small p scattering angles (few rad):
Leading proton detectors in RPs approach beam to 10 + 0.5 mm 1.5 mm
2004 prototype2004 prototype
p. 8Mario Deile –
Proton Detectors: What goes into the Pot?
Need full efficiency as close to the detector edge as possible;adequate resolution ~ 20 m
The edge is itself an electrode.Electrodes processed through the bulk.
SPS testbeam: Effic. transitionwithin ~15m
mm
3D Si Detectors: Planar Si with reduced current-terminating guard structure (only ~70 m):
Efficiency [a.u.]edge
p+
n+
Isurf.
Al
SPS testbeam: Effic. transition within ~60m
p. 9Mario Deile –
TOTEM Beam Optics
Reduce number of bunches (43 and 156) to avoid parasitical interactions downstream.
LTOTEM = 1.6 x 1028 cm-2 s-1 and 2.4 x 1029 cm-2 s-1
Want to measure scattering angles down to a few mrad.
Proton trajectory:
y(s) = Ly(s) y* + vy(s) y*, L(s) = [s]1/2 sin (s)
x(s) = Lx(s) x* + vx(s) x* + Dx(s) ,v(s) = [(s) ]1/2 cos (s)
• Maximise Lx(sRP), Ly(sRP) at sRP of Roman Pot
• Minimise vx(sRP), vy(sRP) at sRP of Roman Pot (parallel-to-point focussing: v = 0)
High- optics: for TOTEM = 1540 m
Consequences:
• low angular spread at IP: *) = / * 0.3 rad• large beam size at IP: * = * 0.4 mm
(if N = 1 m rad)
p. 10Mario Deile –
Running Scenarios
Scenario(goal)
1low |t| elastic,
tot , min. bias
2diffractive physics,
large pT phenomena
3intermediate |t|,
hard diffraction
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 luminosity
[cm-2 s-1]
1.6 x 1028 2.4 x 1029 (1 - 0.5) x 1031 3.6 x 1032
Runs at * = 0.5 m, L = (1033 1034) cm-2 s-1 not yet part of TOTEM programme but under study.
p. 11Mario Deile –
Standalone and with CMS
• Standalone running:
forseen only for elastic scattering and total cross-section.
• Common running: – DAQ and Trigger must be CMS-compatible
(hardware and software)
– TOTEM can act as a CMS subdetector.
– TOTEM can trigger CMS:
Trigger from the Roman Pots must arrive at CMS within the CMS trigger latency:
Very tight for the Pot at 220 m, but still feasible.
Pots farther than 220 m from IP (none foreseen yet) cannot trigger!
p. 12Mario Deile –
Level-1 Trigger Schemes
p
p
p
p
pT1/T2
RP RPCMS
Elastic Trigger:Signal: 500 Hz Background: 20 Hz
Single Diffractive Trigger:Signal: 200 Hz Background: < 1 Hz ? (using vertex reconstruction in T1/T2)
Double Diffractive Trigger:Signal: 100 Hz
Central Diffractive Trigger:Signal: 10 Hz Background: 2 Hz
Minimum Bias Trigger:Signal: 1 kHz
Backgrounds under study!
(L = 1.6 x 1028 cm-2 s-1)
p. 13Mario Deile –
Pomeron exchange ~ e–B|t|
diffractive structure
Photon - Pomeron interference
L dt = 1033 and 1037 cm-2
pQCD ~ |t|–8
Elastic Scattering Cross-Section
p. 14Mario Deile –
Coulomb region 510-4 [lower s, RP closer to beam]Interference, meas. 510-4 510-3 [as above], standard * = 1540 mPomeron exchange 510-3 0.1 * = 1540 mDiffractive structure 0.1 1 * = 1540 m, 18 mLarge |t| – perturb. QCD 1 10 * = 18 m
Region |t| [GeV]2 Running Scenario
Elastic Scattering: t-Acceptance
p. 15Mario Deile –
Elastic Scattering: Resolution
t-resolution (2-arm measurement) -resolution (1-arm measurement)
Test collinearity of particles in the 2 arms Background reduction.
p. 16Mario Deile –
• Current models predictions: 100-130mb
• Aim of TOTEM: ~1% accuracy
Total p-p Cross-Section
mb 1.41.2
2.1 5.111 tot 0058.0
0025.0 .00150 1361.0 LHC:
TE
VA
TR
ON
ISR
UA
4 UA
5
LH
C
Cosmic Rays
COMPETE Collaboration fits:
Ps
sB
s
ss
Yss
Ypppp
tot
2
0
11)( ln
[PRL 89 201801 (2002)]
p. 17Mario Deile –
Measurement of tot
Luminosity-independent measurement of the total cross-section using the Optical Theorem:
02
2
1
16
t
eltot dt
dN
L
ineleltot NN L inelel
teltot NN
dtdN
0
2
)/(
1
16
• Measure the elastic and inelastic rate with a precision better than 1%.• Extrapolate the elastic cross-section to t = 0.
Or conversely:Extract luminosity:
0
22
|/16
1
tel
inelel
dtdN
NN
L
p. 18Mario Deile –
Extrapolation of Elastic Cross-Section to t = 0
Effect Extrapolation uncertainty
Statistics (10h @ 1028): 107 events 0.07 %
Uncertain functional form of d/dt
0.5 %
Beam energy uncertainty 0.05 % 0.1 %
Beam / detector offset 20 m 0.08 %
Crossing angle 0.2 rad 0.1 %
Total 0.53 %
Non-exponential d/dt fitted to
Slope parameter
according to BSW Model
tBftf e)( 0
dtdf
tftB
1
p. 19Mario Deile –
Measurement of the Total Rate Nel + Ninel
[mb]
T1/T2 double arm trigger loss
[mb]
T1/T2 single arm
trigger loss [mb]
Uncertainty after extrapolation
[mb]
Minimum bias 58 0.3 0.06 0.06
Single diffractive 14 - 2.5 0.6
Double diffractive 7 2.8 0.3 0.1
Double Pomeron 1 ~ 0.2
(using leading p and CMS)
0.02
Elastic Scattering 30 - - 0.15
Acceptancesingle diffraction
simulated
extrapolateddetectedLoss at low
masses
Extrapolation of diffractive cross-section to large 1/M2 using d/dM2 ~ 1/M2 .
Total: 0.8 %
p. 20Mario Deile –
Accuracy of tot
%1005.0008.0005.0 222 tot
tot
Extrapolation to t = 0 Total rate Nel + Ninel = 0.12 ± 0.02
p. 21Mario Deile –
~ 90 % of all diffractive protons are seen in the Roman Pots(assuming ).
= p / p can be measured with a resolution of ~ 5 x 10-3 .
Diffraction at high Acceptance
A < 5 %
A > 95 %
85 - 95 %
* = 1540 m
t
dtd
d 10e1
p. 22Mario Deile –
y = – ln
ymax = 6.5
Trigger via Roman Pots > 2.5 x 10-2
Trigger via rapidity gap < 2.5 x 10-2
* = 1540 m: = 0.5% L 2.4 x 1029 cm-2 s-1
* = 200 400 m: ~ 1 ‰ L 1031 cm-2 s-1
* = 0.5 m: ~ 1 ‰ L > 1031 cm-2 s-1
Detection Prospects for Double Pomeron Events
In collaboration with CMS
dN/dy
– ln – ln
y
pp
CMS
CMS + TOTEM
p1
p2 p2’
p1’
PM2 = s
P
* = 0.5 m
p. 23Mario Deile –
Exclusive Production by DPE: Examples
Advantage: Selection rules: JP = 0+, 2+, 4+; C = +1 reduced background, determination of quantum numbers.Good resolution in TOTEM: determine parity: P = (-1)J+1 d/d~ 1 +– cos 2
Particle excl Decay channel BRRate at
2x1029 cm-2 s-1
Rate at
1031 cm-2 s-1
(no acceptance / analysis cuts)
c0
(3.4 GeV)3 b [KMRS]
J/ +–
+ – K+ K–
6 x 10-4
0.018
1.5 / h
46 / h
62 / h
1900 / h
b0
(9.9 GeV)4 nb [KMRS] +– 10-3 0.07 / d 3 / d
H
(120 GeV)
0.1 100 fb
assume 3 fbbb 0.68 0.02 / y 1 / y
Higgs needs L ~ 1033 cm-2 s-1, i.e. a running scenario for = 0.5 m:• try to modify optics for enhanced dispersion,• try to move detectors closer to the beam,• install additional Roman Pots in cold LHC region at a later stage.
p. 24Mario Deile –
Status and Outlook
• TDR was submitted to the LHCC in January • Extensive test-beam programme in summer/autumn
• A TDR on the common CMS/TOTEM physics programme will be submitted in early 2005
p. 26Mario Deile –
GEMs at high luminosities
Test results from COMPASS, HERA-B and LHCb have shown: Rate:
Exposed to 350 MeV π+, π– and p beam (~ 105 / mm2 s) at PSIi.e. rates expected in T2 at L=1033 cm-2 s-1 (incl. background)
Ageing:tests at high rate: no sign of ageing observed after 7 mC / mm2 (equiv. 1011 mip / mm2 or 1 year (107 s) at L=1032 cm-2 s-1)
Time resolution:12.5 ns with Ar/CO2 easily identifies bunches with 75 ns spacing
Sparking:Spark probability measured to be very low at gains of ~104 ,no damage after 5000 sparks
The detector technology is proven and well adapted to the requirements for the T2telescope up to 1033 cm-2 s-1 luminosity.Problem: radiation hardness of the electronics to be tested.
p. 27Mario Deile –
L(s)
High Optics: Lattice Functions
Ly
Lx
vx
vy
v(s)
Parallel-to-point focussing achieved at 220 m (RP station 3) for both x and y !
p. 28Mario Deile –
Dominant background: beam halo: reduction only by 2-arm coincidence.
T1/T2: beam-gas suppression by vertex reconstruction: (r) = 3 mm, (z) = 45 mm
Trigger Logic and Background SuppressionEach Roman Pot houses:• 6 tracking planes (analogue APV 25 readout)• 4 trigger planes (digital VFAT readout)
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