147 research outputs found
Understanding forward B hadron production
No full textAbstract The LHCb collaboration has recently performed a measurement of the production rate of inclusive B hadron production (pp → BX) at both 7 and 13 TeV centre-of-mass (CoM) energies. As part of this measurement, the ratio of these two cross section measurements has been presented differentially in B hadron pseudorapidity within the range of η B ∈ [2.0, 5.0]. A large tension (4σ) is observed for the ratio measurement in the lower pseudorapidity range of η B ∈ [2.0, 3.0], where the data is observed to exceed theoretical predictions, while consistency is found at larger η B values. This behaviour is not expected within perturbative QCD, and can only be achieved by introducing ad-hoc features into the structure of the non-perturbative gluon PDF within the region of x ∈ [10−3 , 10−4]. Specifically, the gluon PDF must grow extremely quickly with decreasing x within this kinematic range, closely followed by a period of decelerated growth. However, such behaviour is highly disfavoured by global fits of proton structure. Further studies of the available LHCb B and D hadron cross section data, available for a range of CoM energies, indicate systematic tension in the (pseudo)rapidity region of [2.0, 2.5]
Phenomenological studies of top quark production in the forward region of phase space at the LHC
No full textThis thesis contains phenomenological studies of top quark production in the forward region of phase space at the Large Hadron Collider (LHC). The production of highly forward top quarks has so far not been observed in nature. As the LHCb detector at the LHC is instrumented in the forward region, this opens the possibility of studying top quark properties in this yet unexplored region of phase space. This feasibility of performing cross section and charge asymmetry measurements of top quark pairs with available and future LHCb data is studied in detail. In both cases, potential analysis strategies are proposed, and sophisticated theoretical predictions are provided for both signal and background. By studying the expected experimental sensitivity of cross section measurements, the potential constraints on parton distribution functions is quantified. The sensitivity of the proposed charge asymmetry measurements with the full Run II LHCb data is also considered
Measuring top quark production asymmetries at LHCb
No full textSimulated data is studied to assess the potential sensitivity of LHCb to measure top quark production asymmetries, via the single particle pseudorapidity asymmetry in muonic decays of top quarks, with current integrated luminosities of 1, 2 fb at 7, 8 TeV LHC centre of mass energies respectively. This includes estimates of reconstruction effects as well as theoretical errors present in signal modelling at the next-to-leading order
Precise predictions for multi-TeV and PeV energy neutrino scattering rates
No full textThis upload contains the main results of the publication Phys.Rev.D 100 (2019) 9, 091301, with arXiv number:1905.03792.
The cross-section results from this article are provided in plain text files, which correspond to the main results of this research. In addition to the published results, a sub-leading contribution (coherent channel) not included in the original publication is also provided which matches the results in the v2 arXiv document.
In summary the files are:
arXiv_1905.03792_fig3.txt: the data for the total mean inelasticity distribution in muon production in (anti)neutrino-nucleon collisions.
arXiv_1905.03792_fig4.txt: the data for the hadronic cross-section in anti-electron neutrino collisions with atomic electrons
arXiv_1905.03792_Resonant_ele_neutron.txt: the cross-section for W-boson production for (anti)-electron neutrino scattering upon neutrons. The calculation includes off-shell effects, as well as various NLO contributions.
arXiv_1905.03792_Resonant_ele_proton.txt: same as above for proton targets.
arXiv_1905.03792_Coherent_ele_A16.txt: the cross-section for W-boson production for (anti)-electron neutrino scattering upon an Oxygen nucleus.
arXiv_1905.03792_DIS_Total_nubar_isoscalar.txt: the Deep Inelastic Scattering (DIS) cross-section rate (including uncertainties) for antineutrino projectiles on an free isoscalar target. This includes the sum of Charged Current and Neutral Current contributions (which are also provided separately). This computation is performed at NNLO QCD + LO QED accuracy.
arXiv_1905.03792_DIS_nuclear_corr_nubar.txt: the corresponding nuclear correction (and uncertainties) to be applied to the above DIS cross-section rate
An explicit Z (')-boson explanation of the B -> K (au) mu (+) mu (-) anomaly
No full textA global fit to the recent B → K* μ + μ - data shows indications for a large new-physics contribution to the Wilson coefficient of the semi-leptonic vector operator. In this article we consider a simple Z′-boson model of 3-3-1 type that can accommodate such an effect without violating any other constraint from quark-flavour physics. Implications for yet unobserved decay modes such as B → X s ν v and longstanding puzzles like B → πK are also discussed. The Z′-boson masses required to address the observed anomaly lie in the range of 7 TeV. Such heavy Z′ bosons evade the existing bounds from precision data and direct searches, and will remain difficult to discover even at a high-luminosity LHC. The potential of an ILC as well as the next generation of low-energy parity-violation experiments in constraining the Z′-boson parameter space is also examined. © 2014 The Author(s)
Asymmetric heavy-quark hadroproduction at LHCb: predictions and applications
No full textAbstract We present a phenomenological analysis of asymmetric bottom- and charm-quark production within the LHCb acceptance relevant for pp collisions at s = 13 TeV. Predictions are provided for both anti-k t bottom- and charm-jet pairs, which are kept differentially with respect to the invariant mass of the jet pair. It is quantified how data in this region can provide sensitivity to the couplings of the Z boson to heavy quarks, and we investigate what precision is needed to compete with LEP. We also discuss how asymmetry and rate measurements can provide constraints on a particular class of new-physics models, which contains gauge bosons with small/moderate couplings to light/heavy quarks and masses of the order of 100GeV. Predictions are obtained including all relevant QCD and QED/weak contributions up to next-to-leading order, which have been implemented in a Fortran code which allows to directly compute the asymmetric cross sections. We provide all relevant analytic formulas for our computations
SMEFT at NNLOPS: production
No full textIn the context of the Standard Model effective field theory (SMEFT) the next-to-next-to-leading (NNLO) QCD corrections to the Higgsstrahlungs () processes in hadronic collisions are calculated and matched to a parton shower (PS). NNLO+PS precision is achieved for the complete sets of SMEFT operators that describe the interactions between the Higgs and two vector bosons and the couplings of the Higgs, a or a boson, and light fermions. A POWHEG-BOX implementation of the computed NNLO SMEFT corrections is provided that allows for a realistic exclusive description of production at the level of hadronic events. This feature makes it an essential tool for future Higgs characterisation studies by the ATLAS and CMS collaborations. Utilising our new Monte Carlo code the numerical impact of NNLO+PS corrections on the kinematic distributions in production is explored, employing well-motivated SMEFT benchmark scenarios.43 pages, 12 figures, 2 tables; v2: revised manuscript published in JHE
The small-x gluon from forward charm production: implications for a 100 TeV proton collider
No full textWe review the constraints on the small-x gluon PDF that can be derived by exploiting the forward D meson production data from the LHCb experiment at √s=5, 7 and 13 TeV. We then discuss the phenomenological implications of the resulting improved small-x gluon for ultra-high energy astrophysics, in particular neutrino telescopes, as well as for the proposed Future Circular Collider (FCC) with √s=100 TeV. We illustrate how at the FCC even electroweak scale cross-sections can become sensitive to the small-x region of the quark and gluon PDFs, and then demonstrate how the addition of the LHCb heavy meson production measurements leads to a reduction of PDF uncertainties for various benchmark cross-sections
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