arXiv subjects

Stephen Farry

Publications and source records attributed to Stephen Farry.

6 recordsLinked to original sources

arXiv2023

Compatibility and combination of world W-boson mass measurements

The compatibility of W-boson mass measurements performed by the ATLAS, LHCb, CDF, and D0 experiments is studied using a coherent framework with theory uncertainty correlations. The measurements are combined using a number of recent sets of parton distribution functions (PDF), and are further combined with the average value of measurements from the Large Electron-Positron collider. The considered PDF sets generally have a low compatibility with a suite of global rapidity-sensitive Drell-Yan measurements. The most compatible set is CT18 due to its larger uncertainties. A combination of all mW measurements yields a value of mW = 80394.6 +- 11.5 MeV with the CT18 set, but has a probability of compatibility of 0.5% and is therefore disfavoured. Combinations are performed removing each measurement individually, and a 91% probability of compatibility is obtained when the CDF measurement is removed. The corresponding value of the W boson mass is 80369.2 +- 13.3 MeV, which differs by 3.6 sigma from the CDF value determined using the same PDF set.

hep-ex↗

arXiv2019

Understanding and constraining the PDF uncertainties in a W boson mass measurement with forward muons at the LHC

Precision electroweak tests are a powerful probe of physics beyond the Standard Model, but the sensitivity is limited by the precision with which the $W$ boson mass ($M_W$) has been measured. The Parton Distribution Function (PDF) uncertainties are a potential limitation for measurements of $M_W$ with LHC data. It has recently been pointed out that, thanks to LHCb's unique forward rapidity acceptance, a new measurement of $M_W$ by LHCb can improve this situation. Here we report on a detailed study on the mechanism driving the PDF uncertainty in the LHCb measurement of $M_W$, and propose an approach which should reduce this uncertainty by roughly a factor of two using LHCb Run 2 data.

hep-ex↗

arXiv2016

Forward EW Physics at the LHC

Measurements of electroweak production in the forward region at the LHC provide unique and complementary information to those performed in the central region. Studies have been performed not just by LHCb, a dedicated forward detector, but also by ATLAS and CMS, which are primarily situated in the central region but can exploit forward calorimetry coverage to contribute to the understanding of SM processes in the forward region.

hep-ex↗

arXiv2016

Observation of Top Quark Production in the Forward Region at LHCb

Forward top production is observed, in the ${\mu}+b$ final state, with the 3 fb$^{-1}$ Run I dataset collected by the LHCb detector. The combined cross-section for $t\bar{t}$ and single top production at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV is measured, for muons from the W boson with $p_{\rm T} > 25$ GeV in the pseudo-rapidity range 2.0$< \eta <$4.5 and with a b-tagged jet with 50$ < p_{\rm T} < 100$ GeV in the pseudorapidity range 2.2$< \eta <$4.2. The production cross-sections are found to be in agreement with NLO predictions.

hep-ex↗

arXiv2015

The PDF4LHC report on PDFs and LHC data: Results from Run I and preparation for Run II

The accurate determination of the Parton Distribution Functions (PDFs) of the proton is an essential ingredient of the Large Hadron Collider (LHC) program. PDF uncertainties impact a wide range of processes, from Higgs boson characterisation and precision Standard Model measurements to New Physics searches. A major recent development in modern PDF analyses has been to exploit the wealth of new information contained in precision measurements from the LHC Run I, as well as progress in tools and methods to include these data in PDF fits. In this report we summarise the information that PDF-sensitive measurements at the LHC have provided so far, and review the prospects for further constraining PDFs with data from the recently started Run II. This document aims to provide useful input to the LHC collaborations to prioritise their PDF-sensitive measurements at Run II, as well as a comprehensive reference for the PDF-fitting collaborations.

hep-ph↗

arXiv2015

The leptonic $W^{\pm}$ boson asymmetry in association with jets at LHCb, and PDF constraints at large-$x$

The unique forward LHCb acceptance opens the possibility for performing precision Standard Model (SM) processes in a kinematical regime beyond the reach of both ATLAS and CMS experiments. In this article we discuss the feasibility of performing $W^{\pm}j$ measurements with 14 TeV LHCb data, and find that the leptonic asymmetry at high pseudorapidity, with appropriate cuts on the associated jet, can provide a factor of three reduction on the $d$ quark PDF uncertainty in a region of Bjorken $x > 0.5$.

hep-ph↗