V. Avati University of Helsinki on behalf of the TOTEM Collaboration cern.ch/Totem/

1. Physics at LHC Prague, 6-12 July 2003 Elastic scattering at TOTEM: optics & detectors V. Avati University of Helsinki on behalf of the TOTEM Collaboration http://www.cern.ch/Totem/

2. Collaboration

3. Historical : CERN Tradition (PS-ISR-SPS) • Dispersion relation fit (logs)g, g=2.20.3 • Current models predictions: 100-130mb • Aim of TOTEM: ~1% accuracy • Absolute calibration of Luminosity The measurement ofstot

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

5. Special optics for the measurement of the forward proton(s) • LOW t measurement  angles ~ 10-2 mrad • At the IP : small beam divergence [sq=(e / b*)1/2]  large b* •  large beam size [sx=(e b* )1/2] • At the detector stations: • y = Lyqy*+ vy y* L = (bb*)1/2 sin m(s) • x = Lx qx *+vx x*+x Dx v= (b/b*)1/2 cos m(s) • Optimal conditions: • parallel to point focussing planes (v=0)  unique position-angle relation • largest Leff sizeable distance to the beam center (~1mm) • lowest emittance (10-6 m. rad ) • Luminosity : 1028 cm-2 sec-1,36 bunches (with b*=1100 m) • An alternative optics (b*=1540m) 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”

6. Ly(1540) vx(1100) Ly(1100) Lx(1100) vx(1540) Lx(1540) vy(1540) vy(1100) High b optics: lattice functions v= (b/b*)1/2 cos m(s) L = (bb*)1/2 sin m(s)

7. Elastic Scattering acceptance b* = 1540 m b* = 1100 m

8. t-acceptance (50%) vs detector position (%) Number of events

9. Errors on the extrapolation to t=0 • Beam angular divergence sq=(e / b*)1/2 • Optical functions • Beam position • Crossing angle • Detector resolution: statistical and systematical (detector offset) • RP station alignement • Background (beam halo, double pomeron exchange…)

10. total beam angular divergence =0 t-resolution (one and two arms) versus detector resolution s(t)/t (1 arm) v dependence! s(t)/t (2 arms) coplanarity

11. Coplanarity test, background rejection: f resolution Detector resolution = 20 mm

12. t=0.004 GeV2 A=44% t=0.01 GeV2 A=67% b=1100m t=0.004 GeV2 A=64.4% t=0.01 GeV2 A=78.2% b=1540m Acceptance dependence from detector offset

13. Elastic Cross section (t=0): stat. and syst. errors L=1028 cm-2 s-1 run time = 4 . 104 sec 10mm detector position uncertainty

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

15. Acceptance b=1540 b=18

16. CMS Hybrid ~3cm 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 ~ 3 x 4 cm2 • Spatial resolution ~ 20 mm • Moderate radiation tolerance (~1014 n /cm2 equiv)

17. Cold Silicon • RD39/NA60 have investigated/used silicon at cryogenic temperatures (~ 100-130 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) 325-329. 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

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

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

20. PLANAR-3D DETECTORS 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

21. 3D DETECTORS AND ACTIVE EDGES Brunel, Hawaii, Stanford • 15 mm InfraRed beam spot • FWHM = 772 mm • Edge Al strip width = 16 mm • INSENSITIVE EDGE • (INCLUDING 16 mm • Al STRIP): • (813 - 772) / 2 = 21 mm • EDGE SENSITIVITY <10 mm • COLLECTION PATHS ~50 mm • SPATIAL RESOLUTION 10-15 mm • DEPLETION VOLTAGES < 10 V • DEPLETION VOLTAGES ~105 V at 1015n/cm2 • SPEED AT RT 3.5 ns • AREA COVERAGE 3X3 cm2 • SIGNAL AMPLITUDE 24 000 e before Irradiation • SIGNAL AMPLITUDE 15 000 e- at 1015n/cm2 • CERN Courier, Vol 43, Number 1, Jan 2003

22. To measure the total cross section with ~ 1% precision • total inelastic rate within 1 % • extrapolation to t=0 within 0.3-0.4 % • Near Future plans: • Optics optimization • Further studies on the systematic • Tests of different forward detectors