First measurement of tot and el

expectations for 2011/12

LHCC 21 Sept 2011

Karsten Eggerton behalf of the TOTEM Collaboration

p. 2 Karsten Eggert–

Elastic scattering differential cross-section

* = 3.5 m, Oct. 2010 (EPL 95 2011, 41001)

Extend the measurement to lower |t| values

p. 3 Karsten Eggert–

Total Cross-Section Measurement

0

2

22

1

16

t

ELTOT dt

dc

Optical Theorem:

Use from COMPETE fit:01.008.014.0

Normalisation with luminosity from CMS

Uncertainty ± 4% dt

dN

Ldt

d ELEL 1

Measure d el / dt at lowest possible |t|

p. 4 Karsten Eggert–

First run with the * = 90 m optics and RP insertion

• Two bunches with 1 and 2 x 1010 protons / bunch• Instantaneous luminosity: 8 x 1026 cm-2 s-1

• Integrated luminosity: 1.7 b-1

• Estimated pile-up: ~ 0.5 % • Vertical Roman Pots at 10 from beam center• Trigger rate : ~ 50 Hz• Recorded events in vertical Roman Pots: 66950

Un-squeeze from injection optics

* = 11m to 90m

[Helmut Burkhardt, Andre Verdier]

Very robust optics with high precision

p. 5 Karsten Eggert–

Proton tracks of a single diagonal (left-right coincidences)

Sector 45

Sector 56

y = Ly y + vy y*

x = Lx x + D + vx x*

Lx ~ 0

Sector 56

Sector 45

t = -p2

p/p

Integrated luminosity : 6.2 nbarn-1

Inel. pile-up ~ 0.8 ev/bx_

*=3.5 m *= 90 m

Integrated luminosity : 1.65 barn-1

Inel. pile-up ~ 0.005 ev/bx

p. 6 Karsten Eggert–

Angular Correlations between outgoing protons

• Background negligible < 1%

• Width of correlation band in agreement with beam divergence (~ 2.4 rad)

Ly ~ 260 m Lx ~ 0 - 3 m

p. 7 Karsten Eggert–

Angular difference between the two outgoing protons

y* (proton1) - y* (proton2)] / √ 2

beam divergence *

/ √ 2

p. 8 Karsten Eggert–

Optics, t-scale and acceptance

• Perturbations: optics very robust (Ly ~ sRP), better than:– Θx

*/Θx*=1.3%syst

– Θy*/Θy

*=0.4%syst

• Non-linearities in Θx*(y) reconstruction due to dLx / ds fixed:

(checked via Lx)• t systematics: t / t = 0.8% (low t) up to 2.6% (large |t|)• Acceptance correction factor < 3 at low |t|, based on symmetry

p. 9 Karsten Eggert–

Raw t-Distributions

Acceptance correctedComparison of the two diagonals

p. 10 Karsten Eggert–

Efficiency Correction and Resolution Unfolding

Trigger efficiency ~ 99.9 %

Reconstruction efficiency ~ 91 %

Unfolding correction

Effect on slope: B=0.11 GeV-2

p. 11 Karsten Eggert–

Final Differential Cross-Section

mb 8.24mb 5.16mb 3.8σ (measured))(extrapol.EL

Exponential slope

Extrapolation to t = 0:

Total elastic cross-section:

Good agreement with the measurement

at |t| > 0.36 GeV2 [EPL 95 (2011) 41001]

22

0

GeV / mb10037.5 tdt

d

2

0GeV 1.20

tB

p. 12 Karsten Eggert–

Systematics and Statistics

• t : [0.6÷1.8]%syst optics <1%align. [3.4÷11.9]%stat (before unfolding)

• d/dt : 4%syst lumin 1%syst (acc.+eff.+backg.+tag) 0.7%syst unfold. • B : 1%stat 1%syst from t 0.7%syst from unfolding

• d/dt(t=0) : 0.3%stat 0.3%syst (optics) 4%syst lumin 1%syst (acc.+eff.+backg.+tag)

• ∫d/dt dt : 4%syst lumin 1%syst (acc.+eff.+backg.+tag) 0.8%stat extrap.

• TOT : (+0.8% ; 0.2%)syst 0.2%stat 2.7%syst = (+2.8% ; 2.7%)syst 0.2%stat

• EL : 5%syst 0.8%stat

• INEL : (+2.4% ; 1.8%)syst 0.8%stat

p. 13 Karsten Eggert–

Results

mb 0.6 73.5 (syst)1.83.1

(stat) eltotinel

inel (CMS) = (68.0 2.0(syst) 2.4(lumi) 4.0 (extrap)) mbinel (ATLAS) = (69.4 2.4(exp) 6.9 (extrap)) mb

Elastic diff. cross-section at optical point:

Elastic exponential slope:

Optical Theorem, 01.008.014.0

mb 8.20.2 8.24mb 5.16mb 3.8σ (syst)(stat)(measured))(extrapol.el

p. 14 Karsten Eggert–

Energy dependence of the exponential slope B

p. 15 Karsten Eggert–

Energy dependence of the elastic and total cross-sections

p. 16 Karsten Eggert–

Energy dependence of inelastic cross-sections

p. 17 Karsten Eggert–

Running Strategy for 2011/12

RP alignment was performed at * = 1.5 m

by approaching the RP detectors to the sharp beam edges produced by the LHC collimatorsQualification for running at * = 1 m, obtained via loss maps

* = 90 m

29. June : machine test run and first RP insertion to 10 using alignment at * = 1.5 m

30 min of data taking first measurement of

t

o

t

August : alignment of all vertical RPs, beam lost before hor. Alignment

No data taking

Plan for end of September:

5 hours data taking at 5 (vertical RP) luminosity independent measurement

Horizontal alignment

October: at least one more run with 147 m alignment diffraction

2012:

Toward larger * ~ 1 km

p. 18 Karsten Eggert–

Acknowledgements

Thanks to:

The LHC crew

for giving us such a beautiful machine

for supporting continuously our TOTEM requests

The physics coordinator Massi Ferro-Luzzi

for his help in critical situations and not forgetting us

The Optics group

for the development of the magic 90m optics

The CMS collaboration

For the friendly collaboration and the luminosity measurement

All our friends, funding agencies and the CERN management