No Arabic abstract
We analyze collider signatures of massive color-octet bosons whose couplings to quarks are suppressed. Gauge invariance forces the octets to couple at tree level only in pairs to gluons, with a strength set by the QCD gauge coupling. For a spin-1 octet, the cross section for pair production at hadron colliders is larger than that for a quark of equal mass. The octet decays into two jets, leading to a 4-jet signature with two pairs of jets forming resonances of the same mass. For a spin-0 octet the cross section is smaller, and the dominant decay is into bbar{b}, or tbar{t} if kinematically allowed. We estimate that discovery of spin-1 octets is possible for masses up to 330 GeV at the Tevatron, and 1 TeV at the LHC with 1 fb^{-1}, while the reach is somewhat lower for spin-0 octets.
This paper explores the physics reach of the proton-proton Future Circular Collider (FCC-hh) and of the High-Energy LHC (HE-LHC) for searches of new particles produced in the $s$-channel and decaying to two high-energy leptons, jets (non-tops), tops or W/Z bosons. We discuss the expected discovery potential and exclusion limits for benchmark models predicting new massive particles that result in resonant structures in the invariant mass spectrum. We also present a detailed study of the HE-LHC potential to discriminate among different models, for a $Z$ that could be discovered by the end of High-Luminosity LHC (HL-LHC).
We investigate the prospects for the discovery of neutral Higgs bosons with a pair of muons by direct searches at the CERN Large Hadron Collider (LHC) as well as by indirect searches in the rare decay $B_s to mu^+mu^-$ at the Fermilab Tevatron and the LHC. Promising results are found for the minimal supersymmetric standard model, the minimal supergravity (mSUGRA) model, and supergravity models with non-universal Higgs masses (NUHM SUGRA). For $tanbeta simeq 50$, we find that (i) the contours for a branching fraction of $B(B_s to mu^+mu^-) = 1 times 10^{-8}$ in the parameter space are very close to the $5sigma$ contours for $pp to bphi^0 to bmu^+mu^- +X, phi^0 = h^0, H^0, A^0$ at the LHC with an integrated luminosity ($L$) of 30 fb$^{-1}$, (ii) the regions covered by $B(B_s to mu^+mu^-) ge 5times 10^{-9}$ and the discovery region for $bphi^0 to bmu^+mu^-$ with 300 fb$^{-1}$ are complementary in the mSUGRA parameter space, (iii) in NUHM SUGRA models, a discovery of $B(B_s to mu^+mu^-) simeq 5times 10^{-9}$ at the LHC will cover regions of the parameter space beyond the direct search for $bphi^0 to bmu^+mu^-$ with $L = 300$ fb$^{-1}$.
Since the W and Z discovery, hadron colliders have provided a fertile ground, in which continuously improving measurements and theoretical predictions allow to precisely determine the gauge boson properties, and to probe the dynamics of electroweak and strong interactions. This article will review, from a theoretical perspective, the role played by the study, at hadron colliders, of electroweak boson production properties, from the better understanding of the proton structure, to the discovery and studies of the top quark and of the Higgs, to the searches for new phenomena beyond the Standard Model.
In this study we investigated indirect manifestations of color octet electron at the next generation linear colliders: International Linear Collider (ILC) and Compact Linear Collider (CLIC). Namely, production of two gluons via color octet electron exchange is considered. Signal and background analysis have been performed taking into account initial state radiation and beamstrahlung. We show that color octet electron (e_(8)) manifestation will be seen upto M(e_(8))=1.75 TeV and 1.70 TeV at ILC and CLIC with sqrt(s)=0.5 TeV, respectively. CLIC with sqrt(s)=3 TeV will be sensitive upto M(e_(8))=6.88 TeV.
We discuss the spin properties of top quark pairs produced at hadron colliders at next-to-leading order in the coupling constant alpha_s of the strong interaction. Specifically we present, for some decay channels, results for differential angular distributions that are sensitive to t tbar spin correlations.