Raffaele Gerosa

Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy (ETmiss). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirect-detection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of ETmiss signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called 2HDM+a, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the 2HDM+a model is presented, including a discussion of the rich and intricate pattern of mono-X signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the 2HDM+a model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the 2HDM+a model that derive from DD, ID and the DM relic density.

Dark matter (DM) simplified models are by now commonly used by the ATLAS and CMS Collaborations to interpret searches for missing transverse energy ($E_T^\mathrm{miss}$). The coherent use of these models sharpened the LHC DM search program, especially in the presentation of its results and their comparison to DM direct-detection (DD) and indirect-detection (ID) experiments. However, the community has been aware of the limitations of the DM simplified models, in particular the lack of theoretical consistency of some of them and their restricted phenomenology leading to the relevance of only a small subset of $E_T^\mathrm{miss}$ signatures. This document from the LHC Dark Matter Working Group identifies an example of a next-generation DM model, called $\textrm{2HDM+a}$, that provides the simplest theoretically consistent extension of the DM pseudoscalar simplified model. A comprehensive study of the phenomenology of the $\textrm{2HDM+a}$ model is presented, including a discussion of the rich and intricate pattern of mono-$X$ signatures and the relevance of other DM as well as non-DM experiments. Based on our discussions, a set of recommended scans are proposed to explore the parameter space of the $\textrm{2HDM+a}$ model through LHC searches. The exclusion limits obtained from the proposed scans can be consistently compared to the constraints on the $\textrm{2HDM+a}$ model that derive from DD, ID and the DM relic density.

A feasibility study is presented for Vector Boson Scattering measurements in the same-sign WW final state, that can be performed during the high luminosity phase of the LHC. Particular emphasis is given to the expected performances of the detector in different upgrade scenarios, which are compared to each other and to the results attained with the current, aged technology. Presented at LP2015 XXVII International Symposium on Lepton Photon Interactions at High Energies Vector Boson Scattering prospects for High-Luminosity LHC at CMS in the same sign WW final state Raffaele Gerosa∗† INFN and University of Milano Bicocca E-mail: Raffaele.Gerosa@mib.infn.it A feasibility study is presented for Vector Boson Scattering (VBS) measurements in the samesign WW final state in view of the high luminosity phase of the LHC (HL-LHC). Particular emphasis is given to the expected performances of the CMS upgraded detector, which is compared to the results attained with the current aged and non-aged technology. Expected sensitivity to the longitudinal electroweak scattering, the non-unitarized scenario, in which the Higgs boson does not regularize the scattering cross section, and to anomalies in the quartic gauge couplings have been set through dedicated simulation studies. International Symposium on Lepton Photon Interactions at High Energies 17-22 August 2015 University of Ljubljana, Slovenia ∗Speaker. †On behalf of the CMS Collaboration c © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). http://pos.sissa.it/ Vector Boson Scattering in the same sign WW final state at CMS Raffaele Gerosa Precision measurements in the electroweak symmetry breaking (EWSB) sector represent important goals in the context of the high luminosity LHC program. Vector Boson Scattering (VBS) and quartic gauge couplings (QGC) are key aspects of the Standard Model (SM), which remain mainly unexplored after the first run of the LHC collisions. In fact, so far only an evidence for the electroweak WW production has been reported by both ATLAS and CMS experiments [1, 2]. The observed Higgs boson provides a candidate for a simplified EWSB mechanism, where vector bosons acquire mass and a longitudinal degree of freedom through their couplings to the Higgs field. These interactions allow also the unitarization of the scattering amplitudes of longitudinally polarized vector bosons (VLVL → VLVL), preventing the final result to be divergent at high energies [3]. If the SM is just an effective low energy theory, the VBS unitarization will be only partially operated by the Higgs boson and the complete regularization would happen via new physics, which intervenes at a large energy scale. In a large data sample, VBS may be used to determine that scale and possibly resolve different models that could be nearly degenerate at the Higgs pole, while showing different behaviors at higher energies. This poster presents studies of the CMS experiment potential at the HL-LHC inside this context [4]. The VBS signal exhibits when two vector bosons, emitted by a pair of incoming quarks, interact with each other. The two quarks get deflected from the beam direction and originate strong hadronic jets in the detector, called tag-jets, which clearly identify a scattering event. In this way, the HLLHC becomes a vector boson collider, providing access to purely electroweak processes, O(α6 ew) at Leading Order (LO), in a high energy regime. Any new resonances in the VBS invariant mass spectrum or a deviation of data from the SM expectations would be a ground-breaking result, a direct evidence of the new physics scale. The small cross section of the electroweak process, O(α6 ew), and the large contamination due to the production of vector boson pairs in association with two hadronic jets via strong interactions, O(α4 ewα s ), make this analysis very challenging. Moreover, in the harsh experimental conditions of the HL-LHC, an average of about 140 soft QCD interactions (pileup) will overlap with each other during the same beam collision. In this high-occupancy environment, background contamination also arises when hadronic jets are misidentified as leptons ( j-` fake rate), or jets from pileup interactions mimic the properties of VBS ones. For these reasons, the designed upgrade of the CMS detector (Phase-II) presents a new tracking system, extended up to |η |=4, and a new radiation hard and highly granular forward calorimeter, which are beneficial in reducing the j-` fake rate as well as the background produced by pileup events. In this study, only fully leptonic decays of the vector bosons are considered, to select topologies with lower backgrounds at hadron colliders, avoiding ambiguities due to the separation of the tag jets from the vector boson decay products. Projections are presented for same-sign WW scattering (pp→W±W± j j→ 2`±2ν j j). The sensitivity to the same-sign WW electroweak scattering is determined through the measurement of its inclusive and longitudinal cross sections. The sensitivity to a non-unitarized scenario, in which the Higgs boson does not play any role in the VBS, is studied as an indicator for the determination of new strongly-coupled sectors in the theory. Finally, new physics resulting in enhanced VBS cross section at high energy could be due to high-mass scalar resonances or new massive vector bosons, such as those predicted in unified theories. Such additional states would alter the strong interference between the VBS diagrams, leading to strong enhancements at high energy. These effects are described through the effective field theory (EFT) formalism, where dimension-six op-

E stato recentemente mostrato, mediante una serie di studi dettagliati, che i grandi stampi per componenti plastici, fabbricati con l’acciaio UNI-EN-ISO 1.2738 comunemente adottato, presentano microstrutture molto disomogenee e valori di tenacita a frattura piuttosto ridotti, essendo ottenuti da blumi che sono stati pre-bonificati in acciaieria per evitare le deformazioni ed i rischi di frattura dovuti alla bonifica di prodotti semifiniti. In alternativa all’acciaio 1.2738, viene proposto l’impiego di un acciaio indurente per precipitazione, con la seguente composizione chimica nominale (percentuali in peso): C 0,16, Ni 3,2, Mo 3,2, V 0,08, Mn 0,68, Cr 0,15, Si 0,22. Il ciclo produttivo proposto e costituito da un trattamento termico svolto in acciaieria (rivolto ad ottenere una microstruttura bainitica quasi omogenea e rinvenuta a 400 °C), dalla lavorazione meccanica, e da un invecchiamento finale a temperatura inferiore ad A1. Un tale trattamento finale non comporta ne una completa trasformazione di fase della matrice, ne elevati gradienti di temperatura, pertanto causa deformazioni molto ridotte; puo, quindi, esser svolto dopo la lavorazione meccanica. Inoltre, un trattamento di invecchiamento opportuno puo produrre microstrutture e proprieta meccaniche omogenee in stampi grandi e geometricamente complessi. Le microstrutture e le proprieta meccaniche di un blumo, di dimensioni originali 500x1500x2400 mm, sono state esaminate allo stato di fornitura. Inoltre, il meccanismo di rafforzamento e stato esaminato mediante campioni prima sottoposti o alla tempra in aria originale, oppure ad un trattamento termico preliminare di laboratorio (austenitizzazione/solubilizzazione a 1050 °C, tempra in acqua, doppio rinvenimento a 400 °C), e poi invecchiati a 470, 510 e 550 °C per durate fino ad 8 ore. Campioni in diverse condizioni di trattamento termico (svolto in acciaieria oppure in laboratorio) sono stati sottoposti a osservazioni microstrutturali (mediante microscopia ottica ed elettronica) ed a prove meccaniche. Sono in corso analisi rivolte a determinare la natura del meccanismo di indurimento, tra cui segnatamente osservazioni mediante microscopia elettronica a scansione ed analisi di diffrazione dei raggi X di precipitati estratti per via elettrochimica.

Recent results on searches for rare decays of the Higgs boson, obtained using 35.9 fb$^{-1}$ of proton-proton collision data collected at ${\sqrt{s} = 13\,\mathrm{TeV}}$ with the CMS detector, are presented. This report includes searches for the Higgs boson decaying into invisible particles, muon pairs, ${\mathrm{J}/\psi\,\gamma}$ and ${\mathrm{Z}\gamma}$ final states. No significant deviations from the standard model predictions have been observed and upper limits are placed on the corresponding decay branching fractions.

In this chapter we will present the results of the impact of radiation on electronics and opto-electronics for two of the LHC experiments during Run 1 and Run 2. ATLAS results are presented in Section 6.1; CMS in Section 6.2. In Section 6.3 we will present a comparison between the two experiments, highlighting operational guidelines and proposing solutions to build the electronics and opto-electronics of the future LHC experiments.