Exclusive Pp Research Articles

Exact two-loop amplitudes for Higgs plus jet production with a cubic Higgs self-coupling

We compute the corrections to the two-loop amplitudes for gg → h, gg → hg, qg → hq, and qq¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ q\\overline{q} $$\\end{document} → hg due to a modified cubic Higgs self-coupling. The exact dependence on the Higgs and top-quark masses across the entire 2 → 2 phase space is determined by numerically solving a system of differential equations for the relevant master integrals. The calculated amplitudes are crucial for evaluating the impact of the considered corrections on exclusive pp → hj production at the hadronic event level. As an application, we calculate the non-universal, kinematic-dependent cubic Higgs self-coupling corrections to the Higgs-boson transverse momentum distribution in gluon-gluon fusion Higgs production for arbitrary values of the transverse momentum.

Study of baryonic resonances and ρ meson production in the reaction pp → ppπ+π− at 3.5 GeV with HADES

We report on measurements of baryon resonance and ρ meson production in the exclusive pp → ppπ+π− channel at a beam kinetic energy of 3.5 GeV measured with the HADES experimental setup. The differential distributions are compared to Monte Carlo simulations based on a resonance model assuming an incoherent sum of contributions of various baryonic resonances with masses below 2 GeV and using inputs from one pion production measured in the same experiment. A very good description of the two pion production is achieved allowing for an estimate of the contribution of one and double baryon-resonance excitation. Using appropriate kinematical cuts the ρ meson signal could also be extracted.

Probing Anomalous Quartic Interactions at the LHC with proton tagging

One of the main goals of the Large Hadron Collider is to find signatures of physics Beyond the Standard Model of particle physics. One way to do this is by studying with high precision the interactions of the Standard Model. In this talk, we address the discovery potential of New Physics in the exclusive channel pp → p X p which relies on the general purpose detectors at the Large Hadron Collider and their respective forward proton detector stations, located at about ~ 210 m w.r.t. the interaction point. These reactions are highly sensitive to quartic electroweak gauge interactions. As a proof of concept, we discuss the exclusive diphoton production at high diphoton invariant mass. We quote sensitivities on the anomalous γγγγ coupling for an integrated luminosity of 300 fb1 at the center-of-mass energy of 14 TeV.We also discuss the discovery potential of 3γZ anomalous quartic gauge coupling by measuring the pp → p(γγ → Zγ)p reaction.

Probing the Charm Quark Yukawa Coupling in Higgs+Charm Production.

We propose a new method for determining the coupling of the Higgs boson to charm quarks, via Higgs production in association with a charm-tagged jet: pp→hc. As a first estimate, we find that at the LHC with 3000 fb^{-1}, it should be possible to derive a constraint of order one, relative to the standard model (SM) value of the charm Yukawa coupling. As a by-product of this analysis, we present an estimate of the exclusive pp→hD^{(*)} electroweak cross section. Within the SM, the latter turns out to be not accessible at the LHC even in the high-luminosity phase.

Lepton-pair production in ultraperipheral collisions at AFTER@LHC

We investigate the potentialities offered by the study of lepton-pair production in ultraperipheral collisions at a fixed-target experiment using the proton and ion LHC beams. In these collisions, exclusive or semi-exclusive lepton-pair production can be used as luminosity monitor as well as a check of the equivalent-photon approximation, via the measurement of the Bethe-Heitler cross section. It can also serve as a probe of the inner hadron structure via the measurement of the lepton-pair azimuthal asymmetry which is sensitive to the timelike virtual Compton scattering. We also briefly discuss the possibility offered by the study of eta(c) production. Finally, we outline the possibilities for lepton-pair production by Pomeron-Odderon fusion in exclusive pp and pA collisions.

FOURTH GENERATION LEPTONS SEARCH IN γγ → ℓ-ℓ+ PROCESS AT THE CERN-LHC

The pp → pXp production is known to be one of the cleanest channels at the Large Hadron Collider (LHC). In this work, we investigate the potential of the exclusive pp → pℓ-ℓ+p process to probe fourth family leptons via anomalous interactions at the LHC by considering three forward detector acceptances: 0.0015 < ξ < 0.5, 0.0015 < ξ <0 .15, and 0.1 < ξ < 0.5. The sensitivity of the model parameters have been obtained at the 95% confidence level.

The measurement of the [formula omitted] reaction near threshold

It is shown that a recent extraction of the total cross section for pp→K+nΣ+ from inclusive K+ production data by the HIRES Collaboration [Phys. Lett. B 692 (2010) 10] is in conflict with experimental data on the exclusive pp→K+pΛ reaction. The HIRES result may be interpreted as an upper bound, which is not inconsistent with the much lower values that already exist in the literature.

Indication of a Deeply Bound and CompactK−ppState Formed in thepp→pΛK+Reaction at 2.85 GeV

We have analyzed data of the DISTO experiment on the exclusive pp --> pLambdaK+ reaction at 2.85 GeV to search for a strongly bound compact K- pp(approximately = X) state to be formed in the pp --> K+ + X reaction. The observed spectra of the K+ missing mass and the pLambda invariant-mass with high transverse momenta of p and K+ revealed a broad distinct peak of 26-sigma confidence with a mass M(X)=2267+/-3(stat)+/-5(syst) MeV/c2 and a width Gamma(X)=118+/-8(stat)+/-10(syst) MeV. The enormously large cross section indicates formation of a compact K- pp with a large binding energy of B(K)=103 MeV, which can be a possible gateway toward cold and dense kaonic nuclear matter.

First exclusive measurements of the K − pp state populated in the pp → K + Λp reaction at 2.85 GeV

We have analyzed data of the DISTO experiment on the exclusive pp to K^+ Lambda p process at T_p = 2.85$ GeV to search for a K^-pp (= X) nuclear bound state to be formed in the pp to K^+ + X reaction. The deviation spectra of the K^+ missing-mass MM (K^+) and Lambda p invariant-mass M(Lambda-p) with selection of large-angle proton emission revealed a structure with M_X = 2265 +- 2 MeV/c2 and Gamma_X = 118 +- 8$ MeV.

Exclusive photoproduction of ϒ: From HERA to Tevatron

The forward photoproduction amplitude for γp→ϒp is calculated in a pQCD k⊥-factorization approach with an unintegrated gluon distribution constrained by inclusive deep-inelastic structure functions. The total cross section for diffractive ϒs is compared with recent HERA data. We also discuss the 2S/1S ratio in diffractive ϒ-production. The amplitude is used to predict the cross section for exclusive ϒ production in hadronic reactions. Differential distributions for the exclusive pp¯→pϒp¯ process are calculated for Tevatron energies. We also show predictions for LHC. Absorption effects are included.

Hunting a light CP-violating Higgs boson via diffraction at the LHC

We study the central diffractive production of the (three neutral) Higgs bosons, with a rapidity gap on either side, in an MSSM scenario with CP-violation. We consider the bb-bar and tautau-bar decay for the light H_1 boson and the four b-jet final state for the heavy H_2 and H_3 bosons, and discuss the corresponding backgrounds. A direct indication of the existence of CP-violation can come from the observation of either an azimuthal asymmetry in the angular distribution of the tagged forward protons (for the exclusive pp -> p+H+p process) or of a sin(2phi) contribution in the azimuthal correlation between the transverse energy flows in the proton fragmentation regions for the process with the diffractive dissociation of both incoming protons (pp -> X+H+Y). We emphasise the advantage of reactions with the rapidity gaps (that is production by the pomeron-pomeron fusion) to probe CP parity and to determine the quantum numbers of the produced central object.

Exclusive $\eta$ production in pp reactions

Angular distributions for the exclusive reaction pp → ppη observed via the π + π − π 0 decay channel have been measured at T beam = 2.15 GeV, 2.50 GeV and 2.85 GeV (excess energies Q = 324 MeV, 412 MeV and 554 MeV). The polar angle of the η shows an anisotropy with respect to the beam direction for the lowest energy, which vanishes for the higher energies. The anisotropy of the pp polar angle increases slightly with the beam energy.

Search for narrow NNπ resonances in exclusive pp→ppπ+π− measurements

Narrow structures in the range of a few MeV have been searched for in ppπ+ and ppπ− invariant mass spectra (Mppπ+ and Mppπ−) obtained from exclusive measurements of the pp→ppπ+π− reaction at Tp=725,750 and 775 MeV using the PROMICE/WASA detector at CELSIUS. The selected reaction is particularly well suited for the search for dibaryon resonances decoupled from NN and/or NΔ. In the mass range 2020 MeV/c2<mdibaryon<2085 MeV/c2 no narrow structures could be identified on the 3σ level of statistical significance neither in Mppπ− nor in Mppπ+ giving an upper limit (95% C.L.) for dibaryon production in this reaction of σ<20 nb.

Correlations between pions of low relative momenta

Two-particle pion correlations in exclusive πp and pp interactions at \(\sqrt s = 2.9 - 4\) GeV are studied in the region of low relative 4-momenta. Relevant correlation functions are obtained with allowance for the results of calculations based on the model of quark-gluon strings and the FRITIOF model. Positive correlations that make it possible to estimate the spatial size of the pion source are observed for pairs of identical pions. No correlations are observed for pairs featuring one charged and one neutral pion.

Λ0 POLARIZATION IN EXCLUSIVE AND INCLUSIVE p-NUCLEUS REACTIONS

Both Λ0 polarization from inclusive and exclusive p-Nucleus reactions follow the same trend as function of xF and [Formula: see text]. It is valid for -1.0&lt;xF&lt;+1.0 and 0.0&lt;PT&lt;2.0 GeV/c and for Nucleus=p, Be, Cu, W and Pb. The value of a depends on the target nature: it is -(0.443 ± 0.037), in exclusive pp reactions; -(0.376 ± 0.024), in inclusive pp reactions; -(0.232 ± 0.012), in inclusive p Be reactions; -(0.124 ± 0.015), in inclusive p Cu reactions; -(0.274 ± 0.023), in inclusive p W reactions; -(0.147 ± 0.023), in inclusive p Pb reactions. It is independent of the beam energy. And this equation is the most simple bilinear form that describes Λ0 polarization in -1.0&lt;xF&lt;+1.0 and 0.0&lt;PT&lt;2.0 GeV/c .

HYPERON-NUCLEON INTERACTIONS IN THE pp→K+Λp REACTION

We present calculations of the invariant mass spectra of the Λp system for the exclusive pp→K+Λp reaction with the aim of studying the final state interaction between the Λ-hyperon and the proton. The reaction is described within a meson exchange framework and the final state Λp interaction is incorporated through an off-shell t-matrix for the Λp→Λp scattering, constructed using the available hyperon-nucleon (YN) potentials. The cross sections are found to be sensitive to the type of YN potential used especially at the Λ and Σ production thresholds. Hence, data on this exclusive reaction, which can be used to constrain the YN potentials are desirable.

Direct determination of two-pion correlations for pp→ 2π+2π− annihilation at rest

We study ππ correlations in the exclusive reaction pp → 2π+2π− at rest measured by the CPLEAR experiment. Avoiding the introduction of an arbitrary reference sample, we analyse differential distributions for equal charge pion pairs removing the phase-space factor event by event. A peak at small relative momenta is most pronounced for large total momentum of the pair. The physical implications of bosonic symmetrization for the properties of the pion source, in particular its radius, are briefly discussed. The two extremes considered are the chaotic Hanbury-Brown-Twiss mechanism and the coherent Skyrmion model.

Single pion production in nucleon-nucleon collisions.

In this work, we explore the NN\ensuremath{\rightarrow}\ensuremath{\pi}NN reaction within a relativistic model for the NN and \ensuremath{\pi}NN coupled systems consistent with two- and three-body unitarity. After describing the theoretical input, we concentrate on some exclusive pp\ensuremath{\rightarrow}pn${\mathrm{\ensuremath{\pi}}}^{+}$ observables. These are compared with the available data and with predictions from other models. In particular, we examine systematically the dependence of some spin observables on various components of the dynamical input. We identify and isolate some problems related to the present approach and we point out possible directions for future research.

A search for glueballs and a study of doouble pomeron exchange at the CERN intersecting storage rings

We present results from a study of centrally produced mesons in 3 × 10 6 events with two small-angle protons at the CERN Intersecting Storage Rings. A high-statistics sample of exclusive pp → pp π + π − events at √ s = 63 GeV has been obtained, where the reaction mechanism is dominated by double pomeron exchange. Scalar or tensor glueballs may be produced by this process. The π + π − mass spectrum has a distinctive structure, and analysis shows that the data are dominantly S-wave up to 1600 MeV. The behaviour of the D-wave provides evidence for a 2 ++ resonance ( M = 1480 ± 50 MeV, Γ = 150 ± 50 MeV) in addition to the f(1270). We also show data on exclusive K + K −, p p, and π +π −π +π − production, and on the analogous reaction αα → ααπ + π − at √ s = 126 GeV. Flavour independence is suggested by the observation of approximately equal numbers of K +K − and π + π − pairs for mass above 1 GeV. The mass spectra are also apparently independent of √ s (45, 63, 126 GeV) and incident particle type (p, α).

Glueball-Glueball interactions and central-hadron production in pp collisions at high energies

Production of resonances in glueball-glueball collisions is studied, and the structure of the K+K-π0 (ηπ+π-) mass distribution in the exclusive central reaction pp → pK+K-π0p (pηπ+π-p) is predicted on the basis of a model in which pseudoscalar (pseudovector) ¦gg〉 state is produced centrally by interactions of two vector-glueballs exchanged in pp collisions.