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.Comment: 18 pages, 17 figures, submitted to EPJ

Emission of Circularly Polarized Terahertz Wave from Inhomogeneous Intrinsic Josephson Junctions

We have theoretically demonstrated the emission of circularly-polarized terahertz (THz) waves from intrinsic Josephson junctions (IJJs) which is locally heated by an external heat source such as the laser irradiation. We focus on a mesa-structured IJJ whose geometry is slightly deviate from a square and find that the local heating make it possible to emit circularly-polarized THz waves. In this mesa, the inhomogeneity of critical current density induced by the local heating excites the electromagnetic cavity modes TM (1,0) and TM (0,1), whose polarizations are orthogonal to each other. The mixture of these modes results in the generation of circularly-polarized THz waves. We also show that the circular polarization dramatically changes with the applied voltage. The emitter based on IJJs can emit circularly-polarized and continuum THz waves by the local heating, and will be useful for various technological application.Comment: 5 pages, 3 figure

LHCb - The LHCb trigger in Run-II

The LHCb Trigger in Run 2 is summarised, with a particular focus on new features such as the Turbo stream and full reconstruction performed in HLT2

Electroweak scale physics & exotic searches at LHCb

The LHCb experiment has a broad and varied physics programme, extending far beyond its core set of flavour physics measurements. This contribution summarises recent electroweak scale measurements and searches for exotic states in the dimuon final state.Comment: 4 pages, 6 figures, contribution to 53th Rencontres de Moriond on QCD and High Energy Interactions (Moriond QCD 2018

Calibration samples for particle identification at LHCb in Run 2

The strategy for data-driven determination of particle identication performance at LHCb has changed signicantly from Run 1 to Run 2 of the LHC. This note outlines these changes, explains the rationale behind them and summarises the new system and conguration

An automated tool to facilitate consistent test-driven development of trigger selections for LHCb’s Run 3

Upon its restart in 2022, the LHCb experiment at the LHC will run at higher instantaneous luminosity and utilize an unprecedented full-software trigger, promising greater physics reach and efficiency. On the flip side, conforming to offline data storage constraints becomes far more challenging. Both of these considerations necessitate a set of highly optimised trigger selections. We therefore present HltEfficiencyChecker: an automated extension to the LHCb trigger application, facilitating trigger development before data-taking driven by trigger rates and efficiencies. Since the default in 2022 will be to persist only the event’s signal candidate to disk, discarding the rest of the event, we also compute efficiencies where the decision was due to the true MC signal, evaluated by matching it to the trigger candidate hit-by-hit. This matching procedure – which we validate here – demonstrates that the distinction between a “trigger” and a “trigger-on-signal” is crucial in characterising the performance of a trigger selection