1. LHC/HERA workshop, WG 4 (17. Jan. 2005)
Startup running of a combined CMS-TOTEM trigger
Karsten Eggert
CERN, PH Department
on behalf of the
TOTEM/CMS Collaboration
LHC/HERA workshop, WG 4 (17. Jan. 2005)

2. T1: 3.1 < h < 4.7
T2: 5.3 < h < 6.5
Optical Theorem

3. CMS + TOTEM: Acceptance
CMS+TOTEM: largest acceptance detector ever built at a hadron collider
> 90 % of all diffractive protons are detected
10 million min. bias events, including all diffractive processes, in a 1 day run with b* = m
microstation at 19m ?
RPs
Total TOTEM/CMS acceptance (b*=1540m)
Roman Pots
TOTEM+CMS
T1,T2
Charged particles
dNch/dh
Energy
flux
dE/dh

4. Elastic Scattering
b* = 1540 m
acceptance

5. Elastic Scattering Cross-Section
Photon - Pomeron interference  r
Multigluon (“Pomeron”) exchange  e– B |t|
104 per bin
of 10-3 GeV2
ds/dt [mb / GeV2]
 t  p2 q2
diffractive structure
pQCD
wide range of
predictions
pp 14 TeV
BSW model
-t [GeV2]
b* = 1540 m
L = 1.6 x 1028 cm-2 s-1
(1)
b*=18 m
L = 3.6 x 1032 cm-2 s-1
(2)
~1 day
(1) (2)

6. Diffraction at high b*: Acceptance
Leading protons in diffraction characterized by t = p2 q2 and x = Dp / p
b* = 1540 m,
RP at 220 m:
A > 95 %
~ 90 % of all diffractive protons are seen in the Roman Pots
(assuming ). %
Resolution in x:
b* = 1540 m: () = 5 x (L  2.4 x 1029 cm-2 s-1)

7. CMS / TOTEM : ideal detector to study diffractive and forward physics with proton measurements
Soft and hard diffraction in Single and Double Pomeron Exchange
production of jets, W, J/y, heavy flavours, hard photons
Excellent proton measurement: gap survival
Double Pomeron exchange as a gluon factory
Production of low mass systems (SUSY, c ,D-Y,jet-jet, …)
Glue balls, …
Higgs production ?
Structure functions (parton saturation) with and without detected protons
Forward physics: DCC, particle and energy flow
gg physics
Different running scenarios (b* = 1540, 172, 18, 0.5 m)

8. Running Scenarios 1 2 3 4 Scenario Physics: low |t| elastic,
stot , min. bias, soft diffraction 2
diffraction 3
large |t| elastic 4
hard diffraction
b* [m]
1540 18
172
N of bunches 43
156
2808
N of part. per bunch
0.3 x 1011
( ) x 1011
1.15 x 1011
Half crossing angle [mrad]
150
Transv. norm. emitt. [mm rad]
3.75
RMS beam size at IP [mm]
454 95
294
RMS beam diverg. [mrad]
0.29
5.28
1.7
220 m [GeV2]
2 x 10-3
1.3
2 x 10-2
220 m [GeV2]
0.6 7
Peak luminosity
[cm-2 s-1]
1.6 x 1028
2.4 x 1029
3.6 x 1032
(1 -4) x 1031

9. New optics b*=172 m Ly large (~270 m) tmin =2 x 10-2 GeV2
~90% of all diffractive protons
are seen
Lx ~ 0
q independent
Vertex measured by CMS
x determination with a precision
of few 10 -4

10. tmin ~ 2 x 10-2 GeV2
10 s beam

11. Conclusion on new optics (b*=172 m) - preliminary
Luminosity of 4 x 1031 cm-2 s-1
About 90% of diffractive protons are seen in the RP at 220 m
x resolution of few to 10 -3
q resolution of few mrad
Future:
more detailed studies on acceptance and resolution
further optimization towards higher luminosity

12. Level-1 Trigger Schemes for min. bias physics
(L = 1.6 x 1028 cm-2 s-1) RP
CMS RP
Elastic Trigger:
Signal: Hz
Background: 20 Hz
Single Diffractive Trigger:
Signal: Hz
Background: < 1 Hz ?
(using vertex reconstruction
in T1/T2)
Double Diffractive Trigger:
Signal: Hz
Central Diffractive Trigger:
Signal: Hz
Background: Hz
Minimum Bias Trigger:
Signal: kHz
Backgrounds under study!
T1/T2 p p p p

13. Runs with ~90% detection of diffractive protons
Initial several one day runs with b* = 1540 m and 43 bunches
L = 1.6 x 1028 cm-2 s-1
10 8 min. bias events / day
1000 events / mbarn per day
Trigger combinations: CMS min bias, T1, T2, forward protons
b* = 1540 m and 156 bunches L = 2.4 x 1029 cm-2 s-1
20 events / nbarn per day
central diffraction: p left x p right x central activity
single diffraction: (T1, T2, CMS forward cal.) left x p right
heavy flavours, jets : low pt leptons, min jets
b* = 172 m and 2808 bunches L = 4 x 1031 cm-2 s-1
3000 events / nbarn per day
Trigger combinations: low pt leptons, jets, diffr. protons

14. Exclusive Production by DPE: Examples
Advantage: Selection rules: JP = 0+, 2+, 4+; C = +1
 reduced background, determination of quantum numbers.
Good f resolution in TOTEM: determine parity: P = (-1)J+1  ds/df ~ 1 +– cos 2f
Particle
sexcl
Decay channel BR
Rate at
2x1029 cm-2 s-1
1031 cm-2 s-1
(no acceptance / analysis cuts)
c0
(3.4 GeV)
3 mb [KMRS]
g J/y  g m+m–
p+ p– K+ K–
6 x 10-4
0.018
1.5 / h
46 / h
62 / h
1900 / h
b0
(9.9 GeV)
4 nb [KMRS]
g U  g m+m–
< 10-3
0.07 / d
3 / d H
(120 GeV)
0.1  100 fb
assume 3 fb bb
0.68
0.02 / y
1 / y
Higgs needs L ~ 1033 cm-2 s-1, i.e. a running scenario for b* = 0.5 m:
try to modify optics locally,
try to move detectors closer to the beam,
install additional Roman Pots in cold LHC region at a later stage.

15. High luminosity runs (b*=0.5m) with x>2.5%
L = 0.5 x 1033 cm-2 s-1
Trigger condition 1: jets and leptons x p left x p right
Trigger condition 2 : jets and leptons x p left x gap right
define the trigger thresholds:
2 jets with pt > 40 GeV for the Higgs
2 large pt jets for high mass central diffraction

16. Higgs event Characteristics: dN/dt & xmin
xmin < 0.3% for one side trigger with x max > 2.5%
Totem acceptance
-t < 1 GeV2
x acceptance?
DPE PHOJET (MH = 120 GeV)
DPE PHOJET (MH = 120 GeV)
dN/dt
dN/dxmin
-t (GeV2)
xmin
SN/dt
SN/dxmin
-t (GeV2)
xmin
 dN/dt  exp(6t)
 should detect p’s down to x  10-3

17. Event Characteristics:
Where do the decay b-jets go?
Asymmetric pair of protons
A typical – symmetric - pair of protons
DPE PHOJET (MH = 120 GeV)
DPE PHOJET (MH = 120 GeV)
dN/dhbmax
dN/dhbmax
xpmin  0.002
xpmax  0.02
Symmetric
pairs dominate
Asymmetric
pair of protons
hbmax
hbmax
SN/dhbmax
SN/dhbmax
xpmax  0.02
xpmin  0.002
hbmax
hbmax
 All the b-jets are confined within h 5.

18. Detection Prospects for Double Pomeron Events
In collaboration with CMS
p1’ p1
b* = 1540 m:  = 0.5% L  2.4 x 1029 cm-2 s-1
b* = 172 m :  ~ few L ~ cm-2 s-1
b* = 0.5 m:  ~ 1 ‰ L ~ cm-2 s-1 P
M2 = x1 x2 s P
Dy = – ln x
ymax = 6.5 p2
p2’
b* = 0.5 m p
dN/dy p
– ln x1
– ln x2
CMS + TOTEM
CMS
Trigger via Roman Pots x > 2.5 x 10-2
Trigger via rapidity gap x < 2.5 x 10-2 y

19. Double Pomeron Exchange: Cross-Section
sDPE = 0.5 – 1 mb  (1–2) x 107 events per day at b* = 1540 m, L = 2 x 1029 cm-2 s-1
Events / GeV
10-1 2x
10-2 2x
10-3 2x
10-4
10-5
10-6
200
~ 1 day
(3) , (4)
L = 2x1029, 1031 cm-2s-1
[e from Pomeron trajectory a(t) = 1 + e + a’ t ]