# CMS Forward and small-x QCD Physics Results

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## 2012 Plots and Results:

A new method to measure the inelastic pp cross section has been developed based on the assumption that pile-up events are randomly distributed according to a Poisson probability.

The first measurement is reported of the exclusive two-photon production of muon pairs in proton-proton collisions at 7TeV

In this paper we study the energy flow in the forward detectors, and the correlations of the forward energy flow with the track multiplicity in the central detector using events with centrally produced and bosons, identified with their leptonic decays. The observed forward energy deposits, their correlations and the track multiplicities in the central part of the CMS experiment are compared with different Monte Carlo models

A measurement of the energy flow in the forward region of the CMS detector at the LHC is presented for centre-of-mass energies of 900 GeV and 7000 GeV.

We report on a measurement of the cross section of inclusive forward jets in proton-proton collisions at ~=~7~TeV, with 3.14~pb integrated luminosity. Jets are reconstructed with the anti- algorithm (size ~0.5) in the Hadronic Forward calorimeters at pseudorapidities 3.2 4.7, in the transverse momentum range ~35 -- 150~GeV/c. The measurement is compared to next-to-leading order perturbative Quantum Chromodynamics calculations, to PYTHIA and HERWIG parton shower event generators, as well as to the CASCADE Monte Carlo.

The measurement of the cross section for the production of pairs of jets, with one of them in the central region and the other one in the forward region of the CMS detector at LHC, in proton-proton collision at =~7~TeV, is presented using a luminosity of 3.14~pb. The jets are selected if they have transverse momentum ~35~GeV and axis within pseudorapidity ~4.7. The differential cross sections for the central and forward jets are compared to various Monte Carlo predictions.

* Observation of diffraction in proton-proton collisions at 7~TeV centre-of-mass energies at the LHC
The observation of inclusive diffraction at LHC with the CMS detector at s=7~TeV is presented, along with a comparison of the data with the predictions of the {\sc Pythia6}, {\sc Pythia8} and {\sc Phojet} generators.

• Measurement of the energy flow in the forward region at the LHC
A measurement is presented of the energy flow in the forward region of the CMS detector at the LHC for centre-of-mass energies sqrt(s) of 900 GeV, 2360 GeV and 7000 GeV. The energy flow is measured in two different event classes: in minimum bias events and in events with a hard scale provided by a dijet system at central pseudorapidities and with transverse energy ETjet>8 GeV at sqrt(s) of 900 GeV and 2360 GeV and with ETjet >20 GeV at sqrt(s) of 7000 GeV.

## 2011 Results

Analysis Approved Plots CDS Entry Luminosity Comment
Measurement of the inelastic pp cross section at √s = 7 TeV with the CMS detector FWD-11-001 PAS-11-001 36/pb Journal: PLB, Conference:Moriond2011
Measurement of the inclusive production cross sections for forward jets and for dijet events with one forward and one central jet in pp collisions at √s = 7 TeV CMS-FWD-11-002 PAS-11-002 3.14/pb Journal: JHEP arXiv:1202.0704, Conference:QM2011
Search for central exclusive γγ production and observation of central exclusive e+e− production in pp collisions at √s = 7 TeV FWD-11-004 PAS-11-004 36/pb

## 2010 Results

Analysis Approved Plots CDS Entry Luminosity Comment
Observation of diffraction in proton-proton collisions at 900 and 2360 GeV centre-of-mass energies at the LHC FWD-10-001 PAS-10-001 10/μb, 0.4/μb https://twiki.cern.ch/twiki/bin/view/CMS/InclusiveDiffraction7TeV
Measurement of the energy flow at large pseudorapidity at the LHC at √s=900, 2360 and 7000 GeV FWD-10-002 PAS-10-002
Inclusive forward jet production cross sections in proton–proton collisions at √s = 7 TeV FWD-10-003 PAS-10-003 3.14/pb Conference:Moriond2011
Evidence for hard-diffractive dijet production in pp collisions at √s = 7 TeV FWD-10-004 PAS-10-004 2.7/nb Conference:Moriond2012
Measurement of exclusive γγ → μ+μ− production at √s = 7 TeV CMS-FWD-10-005 PAS-10-005 40/pb Journal: JHEP arXiv:1111.5536, Conference:Moriond2011
Cross section measurement for simultaneous production of a central and a forward jet in proton-proton collisions at √s =7 TeV FWD-10-006 PAS-10-006 3.14/pb Conference:Moriond2011
Observation of diffraction in proton-proton collisions at 7 TeV centre-of-mass energies at the LHC FWD-10-007 PAS-10-007 20/μb
Forward Energy Flow, Central Track Multiplicities and Large Rapidity Gaps in W and Z Boson Events at 7 TeV pp Collisions CMS-FWD-10-008 PAS-10-008 36/pb Journal:EPJC arXiv:1110.0181v1, Conference:Moriond2011
Forward energy flow in the CMS detector CMS-FWD-10-011 PAS-10-011 239/μb, 206/μb Journal JHEP arXiv:1110.0211, Conference:Moriond2011
Measurement of inclusive and exclusive dijet production ratio at large rapidity intervals at √s = 7 TeV FWD-10-014 PAS-10-014 5/pb Journal:EPJC, Conference:EPS2011

## Publications

Topic attachments
I Attachment History Action Size Date Who Comment
gif Figure_006-a.gif r1 manage 40.4 K 2010-06-22 - 12:58 HannesJung
Topic revision: r37 - 2012-04-04 - PierreVanMechelen

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