31 research outputs found

    Unintegrated gluon distributions and Higgs boson production in proton-proton collisions

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    Inclusive cross sections for Higgs boson production in proton-proton collisions are calculated in the formalism of unintegrated gluon distributions (UGDF). Different UGDF from the literature are used. Although they were constructed in order to describe the HERA deep-inelastic scattering F2F_2 data, they lead to surprisingly different results for Higgs production. We present both two-dimensional invariant cross section as a function of Higgs rapidity and transverse momentum, as well as corresponding projections on rapidity or transverse momentum. We quantify the differences between different UGD's by applying different cuts on interrelations between transverse momentum of Higgs and transverse momenta of both fusing gluons. We focus on large rapidity region. The interplay of the gluon-gluon fusion and weak-boson fusion in rapidity and transverse momentum is discussed. We find that above pTp_T \sim 50-100 GeV the weak-gauge-boson fusion dominates over gluon-gluon fusion.Comment: 32 pages, 18 figures, corrected version, restructured, misprints removed, discussion added, new figure added, in print in EPJ

    How local crustal thermal properties influence the amount of denudation derived from low temperature thermochronometry

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    ranslating amounts and rates of rock cooling derived from low-temperature thermochronometry into denudation requires assumptions about the local geothermal gradient. The temperature gradient in the crust depends on many factors, including basal heat flow, crustal heat production, and thermal conductivity. Consequently, geothermal gradients may be variable on time scales over which rock cooling is tracked by thermochronometry. Using one-dimensional numerical modeling of heat transfer in rocks of varying thermal characteristics, we show that the geothermal gradient of the eroded layer is the most important factor for accurate estimation of denudation amounts. Using a three-dimensional numerical model (Pecube), we demonstrate the impact of crustal heat production and thermal conductivity on estimates of total denudation derived from apatite fission track data from central west Britain. We show that the regional variation in cooling ages measured in Caledonian granites can be explained by geothermal gradient variation due to the presence of a heat-producing granite batholith and removal of insulating sedimentary rocks, and does not require variable denudation. Neglecting the blanketing effect leads to twofold overestimation of the amount of denudation. The occurrence of heat-producing basement that was once covered by a sedimentary blanket is common, in particular in the core of mountain belts. Accurate determination of the amount and rate of denudation from thermochronometric studies in these situations must take into account the composition of the eroded rocks

    Subdominant terms in the production of ccˉc \bar c pairs in proton-proton collisions

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    At high-energies the gluon-gluon fusion is the dominant mechanism of ccˉc \bar c production. This process was calculated in the NLO collinear as well as in the kt_t-factorization approaches in the past. We show that the present knowledge of gluon distributions does not allow to make a precise predictions for ccˉc \bar c production at LHC, in particular at forward rapidities. In this paper we study production of ccˉc \bar c pairs including several subleading mechanisms. This includes: ggQQˉgg \to Q \bar Q, γgQQˉ\gamma g \to Q \bar Q, gγQQˉg \gamma \to Q \bar Q, γγQQˉ\gamma \gamma \to Q \bar Q. In this context we use MRST-QED parton distributions which include photon as a parton in the proton as well as elastic photon distributions calculated in the equivalent photon approximation. We present distributions in the cc quark (cˉ\bar c antiquark) rapidity and transverse momenta and compare them to the dominant gluon-gluon fusion contribution. We discuss also inclusive single and central diffractive processes using diffractive parton distribution found from the analysis of HERA diffractive data. As in the previous case we present distribution in cc (cˉ\bar c) rapidity and transverse momentum. Finally we present results for exclusive central diffractive mechanism discussed recently in the literature. We show corresponding differential distributions and compare them with corresponding distributions for single and central diffractive components.Comment: 20 pages, 19 figure

    Nonphotonic electrons at RHIC within ktk_t-factorization approach and with experimental semileptonic decay functions

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    We discuss production of nonphotonic electrons in proton-proton scattering at RHIC. The distributions in rapidity and transverse momentum of charm and bottom quarks/antiquarks are calculated in the ktk_t-factorization approach. We use different unintegrated gluon distributions from the literature. The hadronization of heavy quarks is done by means of Peterson and Braaten et al. fragmentation functions. The semileptonic decay functions are found by fitting recent semileptonic data obtained by the CLEO and BABAR collaborations. We get good description of the data at large transverse momenta of electrons and find a missing strength concentrated at small transverse momenta of electrons. Plausible missing mechanisms are discussed.Comment: 16 pages, 11 figure

    Exclusive DDˉD \bar D meson pair production in peripheral ultrarelativistic heavy ion collisions

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    The cross sections for exclusive D+DD^+D^- and D0D0ˉD^0 \bar {D^0} meson pair production in peripheral nucleus - nucleus collisions are calculated and several differential distributions are presented. The calculation of the elementary γγDDˉ\gamma \gamma \to D \bar D cross section is done within the heavy-quark approximation and in the Brodsky- Lapage formalism with distribution amplitudes describing recent CLEO data on leptonic D+D^+ decay. Realistic (Fourier transform of charge density) charge form factors of nuclei are used to generate photon flux factors. Absorption effects are discussed and quantified. The cross sections of a few nb are predicted for RHIC and of a few hundreds of nb for LHC with details depending on the approximation made in calculating elementary γγDDˉ\gamma \gamma \to D \bar D cross sections.Comment: 11 pages, 8 figure

    Exclusive production of large invariant mass pion pairs in ultraperipheral ultrarelativistic heavy ion collisions

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    The cross section for exclusive production of π+π\pi^+ \pi^- and π0π0\pi^0 \pi^0 meson pairs in ultrarelativistic heavy ion collisions is calculated for LHC energy sNN=\sqrt{s_{NN}} = 3.5 TeV taking into account photon-photon mechanism. We concentrate on the production of large two-pion invariant masses where the mechanism of the elementary γγππ\gamma \gamma \to \pi \pi process is not fully understood. In order to include a size of nuclei we perform calculation in the impact-parameter equivalent photon approximation (EPA). Realistic charge densities are used to calculate charged form factor of 208^{208}Pb nucleus and to generate photon fluxes associated with ultrarelativistic heavy ions. Sizeable cross sections are obtained that can be measured at LHC. The cross section for elementary γγππ\gamma \gamma \to \pi \pi is calculated in the framework of pQCD Brodsky-Lepage (BL) mechanism with the distribution amplitude used to descibe recent data of the BABAR collaboration on pion transition form factor, using hand-bag mechanism advocated to describe recent Belle data as well as tt and uu-channel meson/reggeon exchanges. We present distributions in two-pion invariant mass as well as the pion pair rapidity for the nuclear process.Comment: 13 pages, 10 figure

    Early Cenozoic denudation of central west Britain in response to transient and permanent uplift above a mantle plume

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    Upwelling mantle plumes beneath continental crust are predicted to produce difficult to quantify, modest uplift and denudation. The contribution of permanent and transient components to the uplift is also difficult to distinguish. A pulse of denudation in Britain in the Early Paleogene has been linked, although with some controversy, with the arrival of the proto-Iceland mantle plume. In this contribution we show that combining apatite and zircon (U-Th-Sm)/He and apatite fission track analyses from central west Britain with numerical modeling clearly identifies a pulse of early Cenozoic denudation. The data indicate that rock uplift and denudation were centered on the northern East Irish Sea Basin and 1.0–2.4 km of rocks were removed during the latest Cretaceous-early Paleogene. Uplift and erosion appears to have started a few million years before the earliest magmatism in the region. The regional denudation pattern mirrors the distribution of low-density magmatic rocks that has been imaged in the deep crust. However, the injection of the underplating melt is not enough to account for the total denudation. An additional regional uplift of at least 300 m is required, which is consistent with a transient thermal effect from the hot mantle plume. The rapid exhumation event ceased by ~40 Ma and the data do not require significant Neogene exhumation

    The γγJ/ψJ/ψ\gamma \gamma \to J/\psi J/\psi reaction and the J/ψJ/ψJ/\psi J/\psi pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions

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    We calculate the cross section for the γγJ/ψJ/ψ\gamma \gamma \to J/\psi J/\psi process. Two mechanisms are considered: box (two-loop) diagrams of the order of O(αem2αs2)O(\alpha_{em}^2 \alpha_s^2) and two-gluon exchange of the order of O(αem2αs4)O(\alpha_{em}^2 \alpha_s^4). The first mechanism is calculated in the heavy-quark non-relativistic approximation while the second case we also include the effects of quantum motion of quarks in the bound state. The box contribution dominates at energies close to the threshold (W<W < 15 GeV) while the two-gluon mechanism takes over at W>W > 15 GeV. Including the bound-state wave function effects for the two-gluon exchange mechanism gives a cross section 0.1 - 0.4 pb, substantially smaller than that in the non-relativistic limit (0.4 - 1.6 pb). We also find a strong infrared sensitivity which manifests itself in a rather strong dependence on the mass for the tt-channel gluons. The elementary cross section is then used in the Equivalent Photon Approximation (EPA) in the impact parameter space to calculate the cross section for 208Pb+208Pb208Pb+J/ψJ/ψ+208Pb^{208}Pb+^{208}Pb \to ^{208}Pb + J/\psi J/\psi + ^{208}Pb reaction. Distributions in rapidity of the J/ψJ/ψJ/\psi J/\psi pair and invariant mass of the pair are shown.Comment: 15 pages, 11 figure

    The State of Art of Production of Automotive Structural Die Casted Elements

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    Wobec wprowadzenia coraz bardziej rygorystycznych norm emisji spalin, współczesne samochody muszą cechować się coraz mniejszym spalaniem paliwa. Jedną z możliwości osiągnięcia tego celu jest zmniejszenie całkowitej masy auta, co może być uzyskane poprzez wykorzystanie aluminiowych odlewów strukturalnych, stanowiących odpowiedzialne części zawieszenia, stref zgniotu czy też karoserii samochodów. W artykule przedstawiono zarówno przyczyny, dla których odlewy strukturalne stają się coraz bardziej pożądane przez największych producentów motoryzacji na świecie, jak również aktualny stan zagadnienia na temat ich produkcji w procesie ciśnieniowego odlewania aluminium.The paper presents the reasons for structural castings are becoming necessary by major automotive manufacturers in the world, as well as current issues regarding their production by the aluminum die-casting process

    Commentary: The King is Naked – a very subjective look at child and adolescent psychiatry

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    There is a great crisis in child-adolescent psychiatry, but we will not solve it just only by increasing the number of psychiatrists nor the number of psychiatric wards. The young patients described in Agnieszka Wlazło's editorial indeed should not end up in a psychiatry department, but that does not mean they do not need any institutional support at all. In this commentary I would like to add two simple but important remarks: we need a serious discussion of the consequences of childhood trauma and mental problems in adolescence and also a well-functioning prevention system to avoid them
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