Samuel van Beek, Emanuele R. Nocera, Juan Rojo, Emma Slade
SciPost Phys. 7, 070 (2019) ·
published 29 November 2019

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We illustrate how Bayesian reweighting can be used to incorporate the constraints provided by new measurements into a global Monte Carlo analysis of the Standard Model Effective Field Theory (SMEFT). This method, extensively applied to study the impact of new data on the parton distribution functions of the proton, is here validated by means of our recent SMEFiT analysis of the top quark sector. We show how, under welldefined conditions and for the SMEFT operators directly sensitive to the new data, the reweighting procedure is equivalent to a corresponding new fit. We quantify the amount of information added to the SMEFT parameter space by means of the Shannon entropy and of the KolmogorovSmirnov statistic. We investigate the dependence of our results upon the choice of alternative expressions of the weights.
Rabah Abdul Khalek, Shaun Bailey, Jun Gao, Lucian HarlandLang, Juan Rojo
SciPost Phys. 7, 051 (2019) ·
published 17 October 2019

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For the foreseeable future, the exploration of the highenergy frontier will
be the domain of the Large Hadron Collider (LHC). Of particular significance
will be its highluminosity upgrade (HLLHC), which will operate until the
mid2030s. In this endeavour, for the full exploitation of the HLLHC physics
potential an improved understanding of the parton distribution functions (PDFs)
of the proton is critical. The HLLHC program would be uniquely complemented by
the proposed Large Hadron electron Collider (LHeC), a highenergy leptonproton
and leptonnucleus collider based at CERN. In this work, we build on our recent
PDF projections for the HLLHC to assess the constraining power of the LHeC
measurements of inclusive and heavy quark structure functions. We find that the
impact of the LHeC would be significant, reducing PDF uncertainties by up to an
order of magnitude in comparison to stateoftheart global fits. In comparison
to the HLLHC projections, the PDF constraints from the LHeC are in general
more significant for small and intermediate values of the momentum fraction x.
At higher values of x, the impact of the LHeC and HLLHC data is expected to be
of a comparable size, with the HLLHC constraints being more competitive in
some cases, and the LHeC ones in others. Our results illustrate the encouraging
complementarity of the HLLHC and the LHeC in terms of charting the quark and
gluon structure of the proton.
Valerio Bertone, Stefano Carrazza, Nathan P. Hartland, Juan Rojo
SciPost Phys. 5, 008 (2018) ·
published 25 July 2018

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Precision phenomenology at the LHC requires accounting for both higherorder
QCD and electroweak corrections as well as for photoninitiated subprocesses.
Building upon the recent NNPDF3.1 fit, in this work the photon content of the
proton is determined within a global analysis supplemented by the LUXqed
constraint relating the photon PDF to leptonproton scattering structure
functions: NNPDF3.1luxQED. The uncertainties on the resulting photon PDF are at
the level of a few percent, with photons carrying up to 0.5% of the proton's
momentum. We study the phenomenological implications of NNPDF3.1luxQED at the
LHC for DrellYan, vector boson pair, top quark pair, and Higgs plus vector
boson production. We find that photoninitiated contributions can be
significant for many processes, leading to corrections of up to 20%. Our
results represent a stateoftheart determination of the partonic structure of
the proton including its photon component.
SciPost Phys. 3, 036 (2017) ·
published 24 November 2017

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We analyze how maximal entanglement is generated at the fundamental level in
QED by studying correlations between helicity states in treelevel scattering
processes at high energy. We demonstrate that two mechanisms for the generation
of maximal entanglement are at work: i) $s$channel processes where the virtual
photon carries equal overlaps of the helicities of the final state particles,
and ii) the indistinguishable superposition between $t$ and $u$channels. We
then study whether requiring maximal entanglement constrains the coupling
structure of QED and the weak interactions. In the case of photonelectron
interactions unconstrained by gauge symmetry, we show how this requirement
allows reproducing QED. For $Z$mediated weak scattering, the maximal
entanglement principle leads to nontrivial predictions for the value of the
weak mixing angle $\theta_W$. Our results are a first step towards
understanding the connections between maximal entanglement and the fundamental
symmetries of highenergy physics.