Higgs and BSM physics at CLIC

The Compact Linear Collider (CLIC) is an option for a future electron-positron collider operating at centre-of-mass energies from a few hundred GeV up to 3 TeV. This paper discusses the Higgs and BSM physics reach of CLIC operating in several energy stages. The presented results are based on physics benchmark analyses using full detector simulations. The initial stage of operation near the top quark pair production threshold allows to study Higgs boson production in the Higgsstrahlung and WW-fusion processes, resulting in model-independent determinations of the Higgs couplings. High-energy operation, here assumed at 1.4 and 3 TeV, gives access to rarer Higgs decays and production processes such as double Higgs production, which is sensitive to the Higgs self-coupling. In the second part of the paper, examples for direct and indirect new physics searches are given. In both cases, the achievable sensitivities generally rise with the centre-of-mass energy

SM-like Higgs decay into two muons at 1.4 TeV CLIC

The potential for measuring the Standard Model (SM) Higgs boson decay into two muons at a 1.4 TeV CLIC e(+)e(-) collider, presented at ICHEP2014, is addressed in this paper. The study is performed in the full Geant4 detector simulations of CLIC_ILD, taking into consideration all the relevant physics and the beam-induced background processes, as well as the instrumentation of the very forward region to tag forward electrons. In this analysis we show that the branching ratio BR(H - GT mu(+)mu(-)) times the Higgs production cross-section can be measured with 38% statistical accuracy at root s =1.4 TeV using an integrated luminosity of 1.5 ab(-1). This study is part of an ongoing comprehensive Higgs physics benchmark study covering various Higgs production processes and decay modes, currently being carried out to estimate the full Higgs physics potential of CLIC.37th International Conference on High Energy Physics (ICHEP), Jul 02-09, 2014, Valencia, Spai

Measurement of the Higgs decay to electroweak bosons at low and intermediate CLIC energies

In this paper a simulation of measurements of the Higgs boson decay to electroweak bosons in $e^+e^-$ collisions at CLIC is presented. Higgs boson production and subsequent $H\rightarrow ZZ^\ast$ and $H\rightarrow WW^\ast$ decay processes were simulated alongside the relevant background processes at 350 GeV and 1.4 TeV center-of-mass energy. Full detector simulation and event reconstruction were used under realistic beam conditions. The achievable statistical precision of the measured product of the Higgs production cross section and the branching ratio for the analysed decays has been determined.Comment: Talk presented at International Workshop on Future Linear Colliders (LCWS15), Whistler, Canada, 2-6 November 2015, CLICdp-Conf-2016-00

Measurement of σ(HVeVe) x BR(H→ ZZ*) and Higgs production in ZZ fusion at a 1.4 TeV CLIC collider

This paper presents the potential measurement at 1.4 TeV CLIC of the cross-section (times branching ratio) of the Higgs production via WW fusion with the Higgs subsequently decaying in ZZ⇤, s(Hnen¯e)⇥BR(H ! ZZ⇤), and of the Higgs production via ZZ fusion with the Higgs subsequently decaying in bb¯, s(He+e)⇥BR(H ! bb¯). For the H ! ZZ⇤ decay the hadronic final state, ZZ⇤ ! qqq¯ q¯, and the semi-leptonic final state, ZZ⇤ ! qql¯ +l , are considered. The results show that s(Hnen¯e)⇥BR(H ! ZZ⇤) can be measured with a precision of 18.3% and 6% for the hadronic and semi-leptonic channel, respectively. s(He+e)⇥BR(H ! bb¯) can be measured with a precision of 1.7%. This measurement also contributes to the determination of the Higgs coupling to the Z boson, gHZZInternational Workshop on Future Linear Colliders (LCWS14) : October 6-10, Belgrade, 2014

Measurement of the σ x BR(H→ZZ*) at 350 GeV and 3 TeV center-of-mass energies CLIC

In this paper we present results of the determination of the statistical precision of the branching fraction measurement, for Higgs decaying to ∗ pairs at 3 TeV and 350 GeV CLIC. Measurements are simulated with the CLIC_ILD detector model, taking into consideration all relevant physics and beam-induced background processes. It is shown that the product of the branching fraction ( → ∗ ) and the Higgs production cross-section can be measured with a relative statistical uncertainty of 3% (20%) at 3 TeV (350 GeV) center-of-mass energy, using semileptonic final states and assuming an integrated luminosity of 5 (1) ab−1 .BPU11 : 11th International Conference of the Balkan Physical Union : Proceedings book; Aug 11 - Sep 1, 2022S05-HEP High Energy Physics (Particles and Fields

Integrated luminosity measurement at CEPC

The very forward region is one of the most challenging regions to instrument at a future $e^+e^-$ collider. At CEPC, machine-detector interface includes, among others, a calorimeter dedicated for precision measurement of the integrated luminosity at a permille level or better. Here we review a feasibility of such precision, from the point of view of luminometer mechanical precision and positioning, beam-related requirements and physics background.A method of the effective center-of-mass determination from $e^+e^- \to \mu^+\mu^-$, initially proposed for FCC, is also discussed for the CEPC beams.Comment: Talk presented at the International Workshop on Future Linear Colliders (LCWS2021), 15-18 March 2021. C21-03-15.1. arXiv admin note: text overlap with arXiv:2010.15061, arXiv:2002.0366

Measurement of the Higgs Branching Ration BR(H→γγH\rightarrow\gamma\gamma) at 3 TeV CLIC

In this paper we address the potential of a 3 TeV center-of-mass energy Compact Linear Collider (CLIC) to measure the Standard Model (SM) Higgs boson decay to two photons. Since photons are massless, they are not coupled to the Higgs boson at the tree level, but they are created in a loop exchange of heavy particles either from the Standard Model or beyond. Any deviation of the effective $H\rightarrow\gamma\gamma$ branching ratio and consequently of the Higgs to photon coupling may indicate New Physics. The Higgs decay to two photons is thus an interesting probe of the Higgs sector, both at the running and future experiments. A similar study has been performed by C. Grefe at 1.4 TeV CLIC, where the statistical uncertainty is determined to be 15\% for an integrated luminosity of 1.5 $ab^{-1}$ with unpolarized beams. \noindent This study is performed using a full simulation of the detector for CLIC and by considering all relevant physics and beam-induced processes in a full reconstruction chain. The measurement is simulated on 5000 samples of pseudo-experiments and the relative statistical uncertainty is extracted from the pull distribution. It is shown that the Higgs production cross-section in $W^+W^-$ fusion times the branching ratio BR($H\rightarrow\gamma\gamma$) can be measured with a relative statistical accuracy of 8.2\%, assuming an integrated luminosity of 5 $ab^{-1}$ with unpolarized beams

CP violation in the Higgs sector at ILC

CP violation is one of Sakharov's condition for the matter-antimatter asymmetry of the Universe. The experimentally observed size of CP violation is insufficient to account for this. Is CP violated in the Higgs sector? Could the SM-like Higgs boson be a mixture of CP even and CP odd states of an extended Higgs sector? With what precision could such effects be measured at future electron-positron colliders? These questions will be discussed in the light of the latest studies at ILC

Measurement of the cross-section for W boson production in association with b-jets in pp collisions at root s=7 TeV with the ATLAS detector

This paper reports a measurement of the W+b-jets (W+b+X and W+b (b) over bar +X) production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb(-1), collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W+b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range. Combining the muon and electron channels, the fiducial cross-section for W+b-jets is measured to be 7.1 +/- 0.5 (stat) +/- 1.4 (syst) pb, consistent with the next-to-leading order QCD prediction, corrected for non-perturbative and double-parton interactions (DPI) contributions, of 4.70 +/- 0.09 (stat) (+0.60)(-0.49) (scale) +/- 0.06 (PDF) +/- 0.16 (non-pert) (+0.52)(-0.38) (DPI) pb