Abstract
Events with no charged particles produced between the two leading jets are studied in proton-proton collisions at sqrt{s}=7,text {TeV}. The jets were required to have transverse momentum p_{mathrm {T}} ^{text {jet}}>40,text {GeV} and pseudorapidity 1.5<|eta ^{text {jet}} |<4.7, and to have values of eta ^{text {jet}} with opposite signs. The data used for this study were collected with the CMS detector during low-luminosity running at the LHC, and correspond to an integrated luminosity of 8,text {pb}^{-1}. Events with no charged particles with p_{mathrm {T}} >0.2,text {GeV} in the interval -1<eta < 1 between the jets are observed in excess of calculations that assume no color-singlet exchange. The fraction of events with such a rapidity gap, amounting to 0.5–1% of the selected dijet sample, is measured as a function of the p_{mathrm {T}} of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky–Fadin–Kuraev–Lipatov evolution equations, including different models of the non-perturbative gap survival probability.
Highlights
In high-energy proton-proton collisions, an interaction with large momentum transfer between two partons may lead to the production of a pair of jets with large transverse momenta pT
The simulation of inclusive dijet events is performed using the pythia 6.422 Monte Carlo (MC) event generator [42]. pythia 6 is based on the leading order (LO) Dokshitzer–Gribov– Lipatov–Altarelli–Parisi (DGLAP) evolution equations combined with a leading-logarithmic (LL) resummation of soft gluon emission in the parton shower, and uses the Lund string fragmentation model [43] for hadroniza
Events with a large rapidity gap between the two leading jets have been measured for the first time at the LHC, for jets with transverse momentum pTjet > 40 GeV and pseudorapidity 1.5 < |ηjet| < 4.7, reconstructed in opposite ends of the detector
Summary
In high-energy proton-proton collisions, an interaction with large momentum transfer between two partons may lead to the production of a pair of jets with large transverse momenta pT. The absence of particles between the jets is reminiscent of a diffractive process [20], in which a color-singlet exchange (CSE) takes place between the interacting partons. The absolute value of the four–momentum squared exchanged in standard diffractive events (less than a few GeV2) is much smaller than that in the events considered here Such events can be understood in a BFKL-inspired approach in terms of the exchange of a color-singlet gluon ladder (Fig. 1), as first discussed by Mueller and Tang in. Jet-gapjet events in proton–proton collisions may be affected by additional scatterings among the spectator partons, which can destroy the original rapidity gap Such a contribution is typically described by a non-perturbative quantity, the socalled gap survival probability, which quantifies the fraction of events where the rapidity gap is not destroyed by interactions between spectator partons [19].
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