The uncertainties in parton distribution functions (PDFs) are the dominant source of the systematic uncertainty in precision measurements of electroweak parameters at hadron colliders (e.g.
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and the mass of the W boson). We show that measurements of the forward–backward charge asymmetry (
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) of Drell–Yan dilepton events produced at hadron colliders provide a new powerful tool to reduce the PDF uncertainties in these measurements.
The uncertainties in Parton Distribution Functions (PDFs) are the dominant source of the systematic uncertainty in precision measurements of electroweak parameters at hadron colliders (e.g. ...\(\sin^2\theta_{eff}(M_Z)\), \(\sin^2\theta_{W}=1-M_W^2/M_Z^2\) and the mass of the W boson). We show that measurements of the forward-backward charge asymmetry (\(A_{FB}(M,y)\)) of Drell-Yan dilepton events produced at hadron colliders provide a new powerful tool to reduce the PDF uncertainties in these measurements.
We show that measurements of the forward-backward charge asymmetry (\(A_{FB}(M,y)\)) of Drell-Yan dilepton events produced at hadron colliders provide a new powerful tool to constrain Parton ...Distribution Functions (PDFs). PDF uncertainties are the dominant source of systematic error in precision measurements at hadron colliders (e.g. \(\chi^2\) values of fits to extract \(\sin^2\theta_{eff}^{lept}(M_Z)\) from \(A_{FB}(M,y)\) with different PDF replicas can be used to place additional constraints on PDFs.In turn, using these constrained PDFs significantly reduces the PDF errors in precision measurements of electroweak parameters. The measurement of the on-shell \(\sin^2\theta_{W}=1-M_W^2/M_Z^2\) is equivalent to an indirect measurement of the W mass. The errors in this indirect measurement of the W mass are competitive with direct measurements. For example, with 200 fb\(^{-1}\) at 13 TeV, the expected error in the indirect measurement of the W mass is \(\pm\)9 MeV.
As part of its HL-LHC upgrade program, the CMS Collaboration is developing a High Granularity Calorimeter (CE) to replace the existing endcap calorimeters. The CE is a sampling calorimeter with ...unprecedented transverse and longitudinal readout for both electromagnetic (CE-E) and hadronic (CE-H) compartments. The calorimeter will be built with \(\sim\)30,000 hexagonal silicon modules. Prototype modules have been constructed with 6-inch hexagonal silicon sensors with cell areas of 1.1~\(cm^2\), and the SKIROC2-CMS readout ASIC. Beam tests of different sampling configurations were conducted with the prototype modules at DESY and CERN in 2017 and 2018. This paper describes the construction and commissioning of the CE calorimeter prototype, the silicon modules used in the construction, their basic performance, and the methods used for their calibration.
The CMS experiment at the CERN LHC will be upgraded to accommodate the 5-fold increase in the instantaneous luminosity expected at the High-Luminosity LHC (HL-LHC). Concomitant with this increase ...will be an increase in the number of interactions in each bunch crossing and a significant increase in the total ionising dose and fluence. One part of this upgrade is the replacement of the current endcap calorimeters with a high granularity sampling calorimeter equipped with silicon sensors, designed to manage the high collision rates. As part of the development of this calorimeter, a series of beam tests have been conducted with different sampling configurations using prototype segmented silicon detectors. In the most recent of these tests, conducted in late 2018 at the CERN SPS, the performance of a prototype calorimeter equipped with \({\approx}12,000\rm{~channels}\) of silicon sensors was studied with beams of high-energy electrons, pions and muons. This paper describes the custom-built scalable data acquisition system that was built with readily available FPGA mezzanines and low-cost Raspberry PI computers.
The successful operation of the Large Hadron Collider (LHC) and the excellent performance of the ATLAS, CMS, LHCb and ALICE detectors in Run-1 and Run-2 with \(pp\) collisions at center-of-mass ...energies of 7, 8 and 13 TeV as well as the giant leap in precision calculations and modeling of fundamental interactions at hadron colliders have allowed an extraordinary breadth of physics studies including precision measurements of a variety physics processes. The LHC results have so far confirmed the validity of the Standard Model of particle physics up to unprecedented energy scales and with great precision in the sectors of strong and electroweak interactions as well as flavour physics, for instance in top quark physics. The upgrade of the LHC to a High Luminosity phase (HL-LHC) at 14 TeV center-of-mass energy with 3 ab\(^{-1}\) of integrated luminosity will probe the Standard Model with even greater precision and will extend the sensitivity to possible anomalies in the Standard Model, thanks to a ten-fold larger data set, upgraded detectors and expected improvements in the theoretical understanding. This document summarises the physics reach of the HL-LHC in the realm of strong and electroweak interactions and top quark physics, and provides a glimpse of the potential of a possible further upgrade of the LHC to a 27 TeV \(pp\) collider, the High-Energy LHC (HE-LHC), assumed to accumulate an integrated luminosity of 15 ab\(^{-1}\).
A measurement of the effective leptonic weak mixing angle
$\sin^2\theta_\mathrm{eff}^\ell$ is presented using the forward-backward
asymmetry in Drell-Yan dilepton events produced in pp collisions at
...$\sqrt{s}=13$ TeV. The data sample corresponds to 137 fb$^{-1}$ of integrated
luminosity and consists of dimuon and dielectron events, including the forward
electrons reconstructed beyond the coverage of the CMS tracking detectors.
Using the CT18Z set of the parton distribution functions (PDF), which provides
the best coverage of the central values extracted with the other global PDFs,
we obtain $$\sin^2\theta^\ell_\mathrm{eff} = 0.23157 \pm 0.00031,$$ where the
total uncertainty includes the statistical uncetainties (0.00010), as well as
the correlated experimental (0.00015), theoretical (0.00009), and PDF (0.00027)
systematic uncertainties. The measured value agrees well with the Standard
Model prediction. This is the most precise measurement at a hadron collider
with comparable precision to the two most precise results obtained at LEP and
SLD.
PDF
