| 1. |
- Lebiedowicz, Piotr, et al.
(författare)
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Diffractive pQCD mechanism of exclusive production of W+W - pairs in proton-proton collisions
- 2012
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Ingår i: Proceedings of Science.
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Konferensbidrag (refereegranskat)abstract
- We present a study of central exclusive production of W+W - pairs in proton-proton collisions at the LHC. We compare the contribution of the γγ → W+W- mechanism with a new mechanism of exclusive diffractive production through the gg → W+W- subprocess with intermediate virtual Higgs boson and quark box diagrams. The amplitude for the latter process is expressed in terms of the off-diagonal unintegrated gluon distribution functions. Several observables related to this process are calculated. The phase space integrated diffractive contribution when separated is only a small fraction of fb compared to 115.4 fb of the γγ-contribution without absorption. This opens a possibility of efficient searches for anomalous boson γW+W - and γγW+W- couplings due to new physics beyond Standard Model.
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| 2. |
- Lebiedowicz, Piotr, et al.
(författare)
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QCD diffractive mechanism of exclusive W+W- pair production at high energies
- 2013
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 867:1, s. 61-81
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Tidskriftsartikel (refereegranskat)abstract
- We discuss new diffractive mechanism of central exclusive production of W+W- pairs in proton-proton collisions at the LHC. We include diagrams with intermediate virtual Higgs boson as well as quark box diagrams. Several observables related to this process are calculated. Predictions for the total cross section and differential distributions in W-boson rapidity and transverse momentum as well as WW invariant mass are presented. We also show results for different polarization states of the final W-+/- bosons. We compare the contribution of the gamma gamma -> W+W- mechanism considered in the literature with the contribution of the diffractive mechanism through the gg -> W(+)W(-)subprocess for the different observables. The phase space integrated diffractive contribution when separated is only a small fraction of fb compared to 115.4 fb of the gamma gamma-contribution without absorption. The latter contribution dominates at small four-momentum transfers squared in the proton lines and in a broad range of W+W- invariant masses. This offers a possibility of efficient searches for anomalous triple-boson (gamma WW) and quartic-boson (gamma gamma WW) couplings and testing models beyond the Standard Model. We discuss shortly also the pp -> pp gamma gamma process, where the box contribution is very similar to that for W+W- and compare our results with recent CDF data. Nice agreement has been achieved without additional free parameters. (C) 2012 Elsevier B.V. All rights reserved.
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| 3. |
- Lebiedowicz, Piotr, et al.
(författare)
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Search for technipions in exclusive production of diphotons with large invariant masses at the LHC
- 2014
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Ingår i: Nuclear Physics, Section B. - : Elsevier BV. - 0550-3213. ; 881, s. 288-308
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Tidskriftsartikel (refereegranskat)abstract
- We focus on exclusive production of neutral technipion (pi) over tilde (0) in pp collisions at the LHC, i.e. on pp -> pp (pi) over tilde (0) reaction. The dependence of the cross section on parameters of recently proposed vector-like Technicolor model is studied. Characteristic features of the differential distributions are discussed. For not too large technipion masses the diphoton decay channel has the dominant branching fraction. This is also the main reason for an enhanced production of neutral technipions in gamma gamma-fusion reaction. We discuss potential backgrounds of the QCD and QED origin to the pp -> pp ((pi) over tilde (0) -> gamma gamma) process at large invariant gamma gamma masses. We conclude that compared to inclusive case the signal-to-background ratio in the considered exclusive reaction is very favorable which thereby could serve as a good probe for Technicolor dynamics searches at the LHC. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).
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| 4. |
- Maciula, Rafal, et al.
(författare)
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Central exclusive quark-antiquark dijet and standard model Higgs boson production in proton-(anti)proton collisions
- 2011
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Ingår i: Physical Review D. Particles and fields. - 0556-2821 .- 1089-4918. ; 83:11
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Tidskriftsartikel (refereegranskat)abstract
- We consider the central exclusive production of q (q) over bar pairs and Higgs boson in proton-proton collisions at LHC. The amplitude for the process is derived within the k(perpendicular to)-factorization approach and considered in different kinematical asymptotics, in particular, in the important high quark transverse momenta and massless quark limits. Quark helicity and spin-projection amplitudes in two different frames are shown in extenso. Rapidity distributions, quark jet p(perpendicular to) distributions, invariant q (q) over bar mass distributions, angular azimuthal correlations between outgoing protons and jets are presented. Irreducible b (b) over bar background to the central exclusive Higgs boson production is analyzed in detail, in particular, how to impose cuts to maximize signal-to-background ratio.
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| 5. |
- Maciula, Rafal, et al.
(författare)
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Exclusive b(b)over-bar pair production and irreducible background to the exclusive Higgs boson production
- 2010
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 82:11, s. 114011-
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Tidskriftsartikel (refereegranskat)abstract
- We calculated the cross section for the exclusive double-diffractive b (b) over bar production in pp -> p(b (b) over bar )p reaction at LHC. Large cross sections are obtained (3-10 nb). This process constitutes the irreducible background to the exclusive Higgs production and is of particular importance in the upcoming Higgs boson searches. The distribution in invariant mass of the b (b) over bar pair is calculated and compared with the corresponding contribution from the Higgs decay. The contribution from the exclusive production of Z(0) and its decay as well as the contribution from the gamma gamma -> b (b) over bar subprocess are also presented for the first time. The influence of cuts on the signal-to-background ratio is discussed.
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| 6. |
- Maciula, Rafal, et al.
(författare)
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New contributions to central exclusive production of dijets in proton-(anti)proton collisions
- 2011
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 84:11
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Tidskriftsartikel (refereegranskat)abstract
- We consider central exclusive production of gg dijets in proton-proton (proton-antiproton) collisions at LHC and Tevatron for different intermediate and final gluon polarizations. The amplitude for the process is derived within the k(perpendicular to)-factorization approach (with both the standard QCD and the Lipatov's effective three-gluon vertices) and is considered in various kinematical asymptotia, in particular, in the important limit of high-p(perpendicular to) jets. Compared to earlier works we include emissions of gluons from different gluonic t-channel lines as well as emission of quark-antiquark dijets. Rapidity distributions, gluon jet p(perpendicular to) distributions and invariant dijet mass distributions are presented. We explore the competition of the standard diagram with both jets emitted from a single t-channel gluon and the one with the emission from both t-channel gluons. The second mechanism requires a special treatment. We propose two different approaches. Including special kinematics and using properties of off-diagonal gluons at small x and xi, we arrive to correlations in two-dimensional distributions in rapidity of one and second jet. We find that the second contribution is much smaller than that known from the literature. The digluon production constitutes an important background to exclusive Higgs production.
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| 7. |
- Pasechnik, Roman, et al.
(författare)
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Central exclusive production of polarised charmonia
- 2011
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Ingår i: Nuclear physics B, Proceedings supplements. - : Elsevier BV. - 0920-5632 .- 1873-3832. ; 214:1, s. 110-113
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Tidskriftsartikel (refereegranskat)abstract
- We consider exclusive double diffractive production of polarised axial-vector chi(c)(1(+)) and tensor chi(c)(2(+)) charmonia in proton-(anti)proton collisions at Tevatron energy. The corresponding amplitudes for these processes are derived within the k(t)-factorisation approach. Contributions from different polarisation states of axial-vector and tensor charmonia are quantified. Corresponding experimental consequences are discussed.
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| 8. |
- Pasechnik, Roman, et al.
(författare)
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Polarization effects in the central exclusive chi(c) production and the J/psi angular distributions
- 2011
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 83:7, s. 074017-
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Tidskriftsartikel (refereegranskat)abstract
- We discuss exclusive elastic double diffractive axial-vector chi(c)(1(+)) and tensor chi(c)(2(+)) mesons production for different meson polarizations in proton-(anti)proton collisions at the Tevatron energy. The amplitude for the process is derived within the k(t)-factorization approach using unintegrated gluon distributions. Differential cross sections for different chi(c) polarizations are calculated. Angular distributions of J/psi meson from the radiative chi(c)(1(+),2(+)) decays are derived. Prospects for experimental selection of different spin states of chi(c) mesons are discussed.
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| 9. |
- Pasechnik, Roman, et al.
(författare)
-
Spin effects in diffractive charmonia production
- 2011
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 26:3-4, s. 583-585
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Tidskriftsartikel (refereegranskat)abstract
- We consider exclusive double diffractive production of polarised axial-vector chi(c)(1(+)) and tensor chi(c)(2(+)) charmonia in proton-(anti)proton collisions at Tevatron energy. The corresponding amplitudes for these processes are derived within the k(t)-factorisation approach. Contributions from different polarisation states of axial-vector and tensor charmonia are quantified. Corresponding experimental consequences are discussed.
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| 10. |
- Szczurek, Antoni, et al.
(författare)
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Diffractive exclusive production of heavy quark pairs at high energy proton-proton collisions
- 2010
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Ingår i: Proceedings of Science.
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Konferensbidrag (refereegranskat)abstract
- We discuss exclusive double diffractive (EDD) production of heavy quark - heavy antiquark pairs at high energies. Differential distributions for cc̄ at √s = 1.96 GeV and for bb̄ at √s = 14 TeV are shown and discussed. Irreducible leading-order bb̄ background to Higgs production is calculated in several kinematical variables. The signal-to-background ratio is shown and several improvements are suggested.
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