1. Xth Blois Workshop on Elastic and Diffractive Scattering
The TOTEM Experiment
V. Avati
CERN, EP Division
on behalf of the
TOTEM Collaboration

2. Collaboration Institut für Luft- und Kältetechnik, Dresden, Germany
CERN, Geneva, Switzerland
Università di Genova and Sezione INFN, Genova, Italy
Institut des Sciences Nucléaires, IN2P3,/CNRS, Grenoble, France
University of Helsinki and HIP, Helsinki, Finland
Warsaw University of Technology,Plock, Poland
Academy of Sciences, Praha, Republic Czech
Brunel University, Uxbridge, UK

3. The measurement of stot
Historical : CERN Tradition (PS-ISR-SPS)
Dispersion relation fit (logs)g , g=2.20.3
Current models predictions: mb
Aim of TOTEM: ~1% accuracy
Absolute calibration of Luminosity

4. -6.5<h<6.5
~150m
~220m
(Optical Theorem)

5. Forward Inelastic Detector
Fully inclusive trigger : loss < 2%
NSD double arm inelastic trigger
- SD single arm inelastic trigger + proton
Reconstruction of the collision vertex to disentangle beam-beam
events from background
Good pattern recognition to identify the tracks
(see talk F. Ferro)

6. T1 Inelastic telescope Measures from η~3.1 to 4.7 on each side
Track chambers CSC
Cathode strip read-out for vertex reconstruction
5 planes on each telescope
Space resolution better than 0.5mm
Trigger by RPC
Two double gap chambers
Pad read-out with projective geometry
Time resolution ~1ns
T1 telescope

7. (In agreement with CMS)
RAILS ARE ASSEMBLED ON A TRUSS STRUCTURE, TO WITHSTAND THE FLEXURAL LOAD
THE TRUSS IS COMPLETELY RESTRAINED ON THE OUTERMOST SPACER RING
PUSH/PULL RODS AT THE END TIE THE 2 TRUSSES AND LIMITS THE TORSION
BASIC SOLUTION: STEEL MADE, ONE TRUSS WEIGHS ROUGHLY 120 Kg
PUSH ROD: COULD BE MADE OF ALUMINIUM OR FIBERGLASS (BETTER PARTICLE TRANSPARENCY) AND/OR ARC-SHAPED
PUSH/PULL RODS
TRUSS
(In agreement with CMS)

8. T2 inelastic telescope
5.32 <h<6.71
13570
400
New T2 design (compatible with CASTOR) with Si detectors
Distance from IP: mm T2 inner radius:33mm
Vacuum chamber inner radius: 25 mm

9. Lightweight Structure
Space for services
 470 mm
Bellow
Thermal Insulation
Weight estimation:
~30 Kg
400 mm

10. General remarks on the “special” optics for the measurement
of the forward proton(s)
y = Ly qy*+ vy y* L = (bb*)1/2 sin m(s)
x = Lx qx *+vx x*+x Dx v= (b/b*)1/2 cos m(s)
LOW t measurement
At the IP : small beam divergence  large b* sq=(e / b*)1/2
 large beam size sx=(e b* )1/2
At the detector stations:
parallel to point focussing planes (v=0)  unique position-angle relation
lowest emittance (10-6 m. rad )
largest Leff  sizeable distance to the beam center (~1mm)
Luminosity : 1028 cm-2 sec-1,36 bunches (with the official baseline b*=1100 m)
An alternative optics (b*=1550m) is under study: interesting feature and better performances
- parallel to point focussing planes in x and y simultaneously at ~220 m
- better “one arm resolution”

11. Elastic Scattering
b* = 1100 m
b* = 1550 m

13. Acceptance
log(-t) (GeV2)
b=1550
b=18

14. Large acceptance : elastic rate and extrapolation t=0
acceptance dependence on detector position
b=1100m
t=0.004 GeV2 A=44%
t= GeV2 A=67%
b=1550m
t=0.004 GeV2 A=64%
t= GeV2 A=78%

15. f and t – resolution versus the azimuthal angle f
coplanarity

16. Elastic Cross section: stat. and syst. errors
L=1028 cm-2 s-1
run time = sec
10mm detector position
uncertainty

17. Large t scattering Ldt = 1033 1037 cm-2
1 eff.day (105sec) at high b and 18 m
-t(GeV2)
15/GeV2
27.103/GeV2
Ldt = cm-2
ds/dt (pp) (mb/GeV2)
(M. Islam)

18. To measure the total cross section with ~ 1% precision
total inelastic rate within 2 %
extrapolation to t=0 within %
importance of systematic: detector position, trigger efficiency,
machine precision (cross angle variation, beam position precision..)

19. Forward Physics First time at a collider a large acceptance detector
TOTEM+CMS+
CASTOR
First time at a collider a large acceptance detector
1 day run at large beta: 10 million minimum bias events, including single and double diffraction
90% of all diffractive protons
are detected
Forward physics important for the
understanding of Cosmic Ray events

21. Diffraction at high b 90% of all diffractive protons
x<10-3
x=0.06
x=0.01
-t=10-2
-t=10-1
log(-t) (GeV2)
90% of all diffractive protons
are seen in the Roman Pots

22. Total TOTEM/CMS acceptance (b*=1550m)
microstation at 19 m ?
RPs

23. Total TOTEM/CMS acceptance (b*=18m)
RPs

24. Detector requirements
High and stable efficiency near the edge facing the beam, edge sharpness < 10 mm
Try to do better than present technology guard rings ~0.5 mm
Detector size is ~3x 4 cm2
Spatial resolution ~20 micron
Moderate radiation tolerance
(~1014 n /cm2 equiv)
~3cm
CMS Hybrid

25. Cold Silicon
RD39/NA60 have investigated/used silicon at cryogenic temperatures (~ K)
Studies hint at possibility of operating silicon microstrip without guard rings at LN temp.
K.Borer et al., “Charge collection efficiency of irradiated silicon detector operated at cryogenic temperatures” NIM A 440 (2000) 5.
L.Casagrande et al.,"A new ultra radiation hard cryogenic silicon tracker for heavy ions beams“ NIM A (2002)
S.Grohman et al., “Detector development for TOTEM Roman Pots”, IX Blois Workshop on El. and Diff. Scatt., Pruhonice, Czech Republic, (2001), 363.
In 2002 we have performed a first measurement on cold edgeless silicon detector
Z. Li et al, "Electrical and TCT characterization of edgeless Si detector diced with different methods", IEEE NSS Proc., San Diego, Nov. 2001

26. Reconstruction of the cut edge
Hits in the telescope
(all good tracks)
Hits in the
cut detector
Efficiency
Edge at: 0+20micron

27. Development with planar technology
cut edge
n+ ring (20 mm) at 30mm from p+
set at the same pot as backplane
hope:
n+ ring stops the C current
B under control with temperature
test of various configuration in summer p+ n+ A B C p+ n+ A B D

28. PLANAR-3D DETECTORS i Edge sensitivity ~20 mm
TRADITIONAL PLANAR DETECTOR
+ DEEP ETCHED EDGE FILLED
WITH POLYSILICON
p + Al
E-field
n + Al i
n + Al
signal a.u.
position [mm]
Edge sensitivity ~20 mm
Leakage current =6nA at 200V
Brunel, Hawaii, Stanford

29. 3D DETECTORS AND ACTIVE EDGES
Brunel, Hawaii, Stanford
EDGE SENSITIVITY <10 mm
COLLECTION PATHS ~50 mm
SPATIAL RESOLUTION mm
DEPLETION VOLTAGES < 10 V
DEPLETION VOLTAGES ~105 V at 1015n/cm2
SPEED AT RT 3.5 ns
AREA COVERAGE X3 cm2
SIGNAL AMPLITUDE e before Irradiation
SIGNAL AMPLITUDE e- at 1015n/cm2
15 mm InfraRed beam spot
FWHM = 772 mm
Edge Al strip width = 16 mm
INSENSITIVE EDGE
(INCLUDING 16 mm
Al STRIP):
( ) / 2 = 21 mm
CERN Courier, Vol 43, Number 1, Jan 2003

30. first prototype ready at the end of 2003
Design of the Roman Pot
Design of the Pot
Design of the Roman Pot Station
Integration in the Tunnel
Main items:
Secondary Vacuum : outgassing and RF shielding
Mechanical Design of a thin window
Integration of detectors inside the pot: mounting, cooling
Design of flange to routing the detector’s services outside the pot
High mechanical precision ( < 20 mm) and reproducibility
first prototype ready at the end of 2003
(see M. Oriunno talk)

31. Roman Pot Device (Second Version)
Compensation bellow
Pot
Lever Arm
Capacitive sensor
Roman Pot Device (Second Version)

33. QRL (LHC Cryogenic Line)4m

34. A novel detector for measuring the leading
protons - the Microstation - is designed to
comply with the LHC requirements.
(M.Ryynänen, R.Orava. /Helsinki group)
a compact and light detector system
integrated with the beam vacuum chamber
geometry and materials compatible with the machine
requirements
mm accuracy in sensor movements
robust and reliable to operate
Si strip or pixel detector technology
Development in cooperation with the LHC machine groups
(see M.Ryynänen talk)

35. Microstation Inch worm motor Emergency actuator 6cm Detector
Inner tube for rf fitting
6cm
Space for cables and cooling link
Detector
Space for encoder
Note: A secondary vacuum
is an option.
M.Ryynänen, R.Orava. /Helsinki group

36. Radiation fluence in the RP silicon detectors (N. Mokhov,I
Radiation fluence in the RP silicon detectors (N.Mokhov,I. Rakhno,Fermilab-Conf-03/086)
Maximum fluence (1014 cm-2) for charged hadrons
(E>100 KeV , L= 1033 cm-2 s-1, t=107s):
RP4 (215 m)  Vertical: 0.58, Horizontal: 6.7
Dose (104 Gy/yr)
RP4 (215 m)  Vertical: (max: 1.9), Horizontal:1.2 (max:55)
Main source of background: pp collisions
Tails from collimators and beam-gas scattering ~ 0.1-1%
Radiation level manageable

37. Running scenario Total Cross Section and Elastic Scattering
Runs with single beams (calibration + background)
Several 1 day runs with b*=1550m (CMS Magnet On/Off)
Several 1 day runs with b*=18m for large-t elastics
Diffraction
Runs with CMS (active or passive trigger) with b*=1550m for L =1028cm-2 s-1
Runs with CMS (active or passive trigger) with b*=0.5m for L < 1033cm-2 s-1

38. consolidation of the collaboration!
Plans:
test of Si detectors ( )
Roman Pot prototype end 2003
trigger studies ( )
TDR end 2003
consolidation of the collaboration!
CMS/TOTEM collaboration for high luminosity diffractive measurements
(see A. De Roeck talk)