2011 QCD and High Energy Interactions - Rencontres de Moriond ...

After Moriond-2011, ATLAS reported the following results from an updated analysis 13 :
σinel(ξ > 10 −6 ) = 60.33 ± 2.10(exp.) ± 0.4 mb (5)
σinel(ξ > m 2 p/s) = 69.4 ± 2.4(exp.) ± 6.9(extr.) mb (6)
Also after Moriond-2011, CMS reported a measurement 14 of σ inel
vtx based on events with 3
or more particles with pT > 200 MeV/c in |η| < 2.4, σ inel
vtx = 59.7 ± 0.1(stat.) ± 1.1(syst.) ±
2.4(Lumi) mb, and using MC models to extrapolate to σ inel
t
obtained:
66.8 ≤ σ inel
t ≤ 74.8 mb. (7)
Both the ATLAS and CMS results are in good agreement with the RENORM prediction.
3 Conclusion
The total pp cross section at the LHC is predicted in a phenomenological approach that obeys
all unitarity constraints. The approach is based on a saturated Froissart bound above a pp
collision energy-squared s = sF , leading to an analytic ln 2 (s/sF )-dependence, σt = (π/so) ·
ln 2 (s/sF ). The scale parameters sF and so are experimentally determined from pre-LHC SD
results. Using the ratio Rel/t ≡ σel/σt from a global fit to cross sections 12 to extract σel from
σt, a σmodel inel = 71 ± 6 mb at √ s = 7 TeV is obtained, which is in agreement with the ATLAS
σinel(ξ > m2 p/s) = 69.4 ± 2.4(exp.) ± 6.9(extr.) mb and the CMS 66.8 ≤ σinel t ≤ 74.8 mb results.
Acknowledgments
Warm thanks to The Rockefeller University and the U.S. Department of Energy Office of Science
for financial support, and to my colleagues at Rockefeller, CDF and CMS for many discussions.
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