We present the first calculation of the high-energy corrections to the process of isolated photon production in association with two jets. These corrections both stabilise the perturbative behaviour in $$ {m}_{j_1{j}_2} $$ and lead to a significantly improved description of data from a recent ATLAS measurement.

United Kingdom

Switzerland

Jeppe Andersen

Spain

Andreas Maier

Malina Rosca

Germany

Giacomo Ruisi

Stable perturbative predictions for isolated photon production with a jet pair at large $$ {m}_{j_1{j}_2} $$

With the discovery of a Higgs boson with a mass of 125 gigaelectronvolts (GeV) at the Large Hadron Collider (LHC) at CERN in 2012, the Standard Model (SM) is complete, and despite intensive searches, no new fundamental particle has been observed since then. In fact, a discovery can be challenging without a predictive new physics model because different channels and observables cannot be combined directly and unambiguously. Furthermore, without supporting indirect hints, the signal space to be searched is huge, resulting in diluted significances owing to the look-elsewhere effect. Several LHC processes with multiple leptons in the final state point towards the existence of a new Higgs boson with a mass between 140 GeV to 160 GeV decaying mostly to $\textit{W}$ bosons. While the former strongly reduces the look-elsewhere effect, the latter indicates that it could be a Higgs triplet with zero hypercharge. Within this simple and predictive extension of the SM, we simulate and combine different channels of di-photon production in association with leptons, missing energy, jets, $\textit{etc}$... Using the full run-2 results by ATLAS, including those presented recently at the Moriond conference, an increased significance of 4 standard deviations is obtained for a $\approx$ 152 GeV Higgs. Due to the previously predicted mass range, the look-elsewhere effect is negligible, and this constitutes the highest statistical evidence for a new narrow resonance obtained at the LHC. Furthermore, the model predicts a heavier-than-expected $\textit{W}$ boson, as indicated by the global electroweak fit. If further substantiated, the discovery of a new Higgs would overthrow the SM, provide a compelling case for the construction of future particle colliders, and pave the way to a novel understanding of the known shortcomings of the SM. In particular, the triplet Higgs field can lead to a strong first-order phase transition and could thus be related to the matter anti-matter asymmetry in our Universe.

Andreas Crivellin

China

Saiyad Ashanujjaman

Sumit Banik

Guglielmo Coloretti

India

Siddharth P. Maharathy

South Africa

Bruce Mellado

Growing evidence for a Higgs triplet * The work of Andreas Crivellin is supported by a Professorship Grant from the Swiss National Science Foundation (PP00P21_76884). The work of Saiyad Ashanujjaman is partially supported by the National Natural Science Foundation of China (11835013). Siddharth P. Maharathy acknowledges using the SAMKHYA: High-Performance Computing Facility provided by the Institute of Physics, Bhubaneswar

We demonstrate that cell resampling can eliminate the bulk of negative event weights in large event samples of high multiplicity processes without discernible loss of accuracy in the predicted observables. The application of cell resampling to much larger data sets and higher multiplicity processes such as vector boson production with up to five jets has been made possible by improvements in the method paired with drastic enhancement of the computational efficiency of the implementation.

Daniel Maître

Efficient negative-weight elimination in large high-multiplicity Monte Carlo event samples

We present all-order predictions for Higgs boson production plus at least one jet which are accurate to leading logarithm in   <math> <mover> <mi>s</mi> <mo>̂</mo> </mover> <mo>/</mo> <msup> <mfenced> <msub> <mi>p</mi> <mo>⊥</mo> </msub> </mfenced> <mn>2</mn> </msup> </math>  $$ \hat{s}/{\left|{p}_{\perp}\right|}^2 $$ . Our calculation includes full top and bottom quark mass dependence at all orders in the logarithmic part, and to highest available order in the tree-level matching. The calculation is implemented in the framework of High Energy Jets (HEJ). This is the first cross section calculated with log(  <math> <mover> <mi>s</mi> <mo>̂</mo> </mover> </math>  $$ \hat{s} $$ ) resummation and matched to fixed order for a process requiring just one jet, and our results also extend the region of resummation for processes with two jets or more. This is possible because the resummation is performed explicitly in phase space. We compare the results of our new calculation to LHC data and to next-to-leading order predictions and find a numerically significant impact of the logarithmic corrections in the shape of key distributions, which remains after normalisation of the cross section.

Hitham Hassan

Jérémy Paltrinieri

United States

Andreas Papaefstathiou

Jennifer Smillie

High energy resummed predictions for the production of a Higgs boson with at least one jet

We propose a novel method for the elimination of negative Monte Carlo event weights. The method is process-agnostic, independent of any analysis, and preserves all physical observables. We demonstrate the overall performance and systematic improvement with increasing event sample size, based on predictions for the production of a W boson with two jets calculated at next-to-leading order perturbation theory.

Unbiased elimination of negative weights in Monte Carlo samples

We present the results of the first calculation of the logarithmic corrections to the QCD contribution to same-sign <math><mi>W</mi></math>-pair production, <math><mi>p</mi><mi>p</mi><mo>→</mo><msup><mi>e</mi><mo>±</mo></msup><msub><mi>ν</mi><mi>e</mi></msub><msup><mi>μ</mi><mo>±</mo></msup><msub><mi>ν</mi><mi>μ</mi></msub><mi>j</mi><mi>j</mi></math>, for same-sign charged leptons. This includes all leading logarithmic contributions which scale as <math><msubsup><mi>α</mi><mi>W</mi><mn>4</mn></msubsup><msubsup><mi>α</mi><mi>s</mi><mrow><mn>2</mn><mo>+</mo><mi>k</mi></mrow></msubsup><msup><mi>log</mi><mi>k</mi></msup><mo>(</mo><mover><mi>s</mi><mo>^</mo></mover><mo>/</mo><msubsup><mi>p</mi><mo>⊥</mo><mn>2</mn></msubsup><mo>)</mo></math>. This process is important for the study of electroweak couplings and hence the QCD contributions are usually suppressed through a choice of vector boson scattering cuts. These select regions of phase space where logarithms in <math><mover><mi>s</mi><mo>^</mo></mover><mo>/</mo><msubsup><mi>p</mi><mo>⊥</mo><mn>2</mn></msubsup></math> are enhanced. While the logarithmic corrections lead to a small change for the cross sections, several distributions relevant for experimental studies are affected more significantly.

Jeppe R. Andersen

Bertrand Ducloué

Conor Elrick

Graeme Nail

Jennifer M. Smillie

Logarithmic corrections to the QCD component of same-sign <math><mi>W</mi></math>-pair production for vector boson scattering studies

Large logarithmic corrections in   <math> <mover> <mi>s</mi> <mo>̂</mo> </mover> <mo>/</mo> <msubsup> <mi>p</mi> <mi>t</mi> <mn>2</mn> </msubsup> </math>  $$ \hat{s}/{p}_t^2 $$  lead to substantial variations in the perturbative predictions for inclusive W-plus-dijet processes at the Large Hadron Collider. This instability can be cured by summing the leading-logarithmic contributions in   <math> <mover> <mi>s</mi> <mo>̂</mo> </mover> <mo>/</mo> <msubsup> <mi>p</mi> <mi>t</mi> <mn>2</mn> </msubsup> </math>  $$ \hat{s}/{p}_t^2 $$  to all orders in α  s . As expected though, leading logarithmic accuracy is insufficient to guarantee a suitable description in regions of phase space away from the high energy limit.

James Black

Australia

Helen Brooks

Emmet Byrne

Combined subleading high-energy logarithms and NLO accuracy for W production in association with multiple jets

We propose the Positive Resampler to solve the problem associated with event samples from state-of-the-art predictions for scattering processes at hadron colliders typically involving a sizeable number of events contributing with negative weight. The proposed method guarantees positive weights for all physical distributions, and a correct description of all observables. A desirable side product of the method is the possibility to reduce the size of event samples produced by General Purpose Event Generators, thus lowering the resource demands for subsequent computing-intensive event processing steps. We demonstrate the viability and efficiency of our approach by considering its application to a next-to-leading order + parton shower merged prediction for the production of a W boson in association with multiple jets.

Christian Gütschow

Sweden

Stefan Prestel

A Positive Resampler for Monte Carlo events with negative weights

We consider top-quark mass effects in the Higgs-interference contribution to <math><mi>Z</mi></math>-boson pair production in gluon fusion. While this production mechanism is formally of next-to-next-to leading order, its contribution is numerically important above the top threshold <math><mrow><msubsup><mrow><mi>M</mi></mrow><mrow><mi>Z</mi><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msubsup><mo>=</mo><mn>4</mn><msubsup><mrow><mi>m</mi></mrow><mrow><mi>t</mi></mrow><mrow><mn>2</mn></mrow></msubsup></mrow></math>. This region is essential to constrain the width of the Higgs boson, and good control over the top-quark mass dependence is crucial. We determine the form factors that are relevant for the interference contribution at two-loop order using a method based on a conformal mapping and Padé approximants constructed from the expansions of the amplitude for large top mass and around the top threshold.

Italy

Ramona Gröber

Thomas Rauh

Top quark mass effects in <math><mi>g</mi><mi>g</mi><mo>→</mo><mi>Z</mi><mi>Z</mi></math> at two loops and off-shell Higgs boson interference

We compute three-loop corrections to the Higgs boson-gluon form factor, incorporating the top quark mass dependence. Our method is based on the combination of expansions around the top threshold and for large top quark mass, using conformal mapping and Padé approximation to describe the form factor over the full kinematic range.

Joshua Davies

Matthias Steinhauser

Top quark mass dependence of the Higgs boson-gluon form factor at three loops