The hints from the LHC for the existence of a $W$ boson of mass around 1.9 TeV point towards a certain $SU(2)_Ltimes SU(2)_Rtimes U(1)_{B-L}$ gauge theory with an extended Higgs sector. We show that the decays of the $W$ boson into heavy Higgs bosons
have sizable branching fractions. Interpreting the ATLAS excess events in the search for same-sign lepton pairs plus $b$ jets as arising from $W$ cascade decays, we estimate that the masses of the heavy Higgs bosons are in the 400--700 GeV range.
We present a renormalizable theory that includes a $W$ boson of mass in the 1.8-2 TeV range, which may explain the excess events reported by the ATLAS Collaboration in a $WZ$ final state, and by the CMS Collaboration in $e^+!e^- jj$, $Wh^0$ and $jj$
final states. The $W$ boson couples to right-handed quarks and leptons, including Dirac neutrinos with TeV-scale masses. This theory predicts a $Z$ boson of mass in the 3.4-4.5 TeV range. The cross section times branching fractions for the narrow $Z$ dijet and dilepton peaks at the 13 TeV LHC are 10 fb and 0.6 fb, respectively, for $M_{Z}= 3.4$ TeV, and an order of magnitude smaller for $M_{Z}= 4.5$ TeV.
Color-singlet gauge bosons with renormalizable couplings to quarks but not to leptons must interact with additional fermions (anomalons) required to cancel the gauge anomalies. Analyzing the decays of such leptophobic bosons into anomalons, I show th
at they produce final states involving leptons at the LHC. Resonant production of a flavor-universal leptophobic $Z$ boson leads to cascade decays via anomalons, whose signatures include a leptonically decaying $Z$, missing energy and several jets. A $Z$ boson that couples to the right-handed quarks of the first and second generations undergoes cascade decays that violate lepton universality and include signals with two leptons and jets, or with a Higgs boson, a lepton, a $W$ and missing energy.
Assuming that dark matter particles interact with quarks via a GeV-scale mediator, we study dark matter production in fixed target collisions. The ensuing signal in a neutrino near detector consists of neutral-current events with an energy distributi
on peaked at higher values than the neutrino background. We find that for a $Z$ boson of mass around a few GeV that decays to dark matter particles, the dark matter beam produced by the Main Injector at Fermilab allows the exploration of a range of values for the gauge coupling that currently satisfy all experimental constraints. The NO$ u$A detector is well positioned for probing the presence of a dark matter beam, while future LBNF near-detectors would provide more sensitive probes.
We study a dynamical mechanism that generates a composite vectorlike fermion, formed by the binding of an $N$-tuplet of elementary chiral fermions to an $N$-tuplet of scalars. Deriving the properties of the composite fermion in the large $N$ limit, w
e show that its mass is much smaller than the compositeness scale when the binding coupling is near a critical value. We compute the contact interactions involving four composite fermions, and find that their coefficients scale as $1/N$. Physics beyond the Standard Model may include composite vectorlike fermions arising from this mechanism.
The CMS Collaboration has recently reported some excess events in final states with electrons and jets, in searches for leptoquarks and $W$ bosons. Although these excesses may be due to some yet-to-be-understood background mismodeling, it is useful t
o seek realistic interpretations involving new particles that could generate such events. We show that resonant pair production of vector-like leptons that decay to an electron and two jets leads to kinematic distributions consistent with the CMS data.
We explore quark interactions mediated by new gauge bosons of masses in the 0.3 - 50 GeV range. A tight upper limit on the gauge coupling of light Z bosons is imposed by the anomaly cancellation conditions in conjunction with collider bounds on new c
harged fermions. Limits from quarkonium decays are model dependent, while electroweak constraints are mild. We derive the limits for a Z boson coupled to baryon number, and then construct a Z model with relaxed constraints, allowing quark couplings as large as 0.2 for a mass of a few GeV.
Using the LHC and Tevatron data, we set upper and lower limits on the total width of the Higgs-like boson. The upper limit is based on the well-motivated assumption that the Higgs coupling to a W or Z pair is not much larger than in the Standard Mode
l. These width limits allow us to convert the rate measurements into ranges for the Higgs couplings to various particles. A corollary of the upper limit on the total width is an upper limit on the branching fraction of exotic Higgs decays. Currently, this limit is 47% at the 95% CL if the electroweak symmetry is broken only by doublets.
The Higgs boson decay into a pair of real or virtual W bosons, with one of them decaying leptonically, is predicted within the Standard Model to have the largest branching fraction of all Higgs decays that involve an isolated electron or muon, for M_
h > 120 GeV. We compute analytically the fully-differential width for this h -> l u jj decay at tree level, and then explore some multi-dimensional cuts that preserve the region of large signal. Future searches for semileptonic decays at the Tevatron and LHC, employing fully-differential information as outlined here, may be essential for ruling out or in the Higgs boson and for characterizing a Higgs signal.
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 oct
et, 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.
