Related papers: Macroscopic Strings and "Quirks" at Colliders
The existence of new coloured states with spin one-half, i.e. extra-quarks, is a striking prediction of various classes of new physics models. Should one of these states be discovered during the 13 TeV runs of the LHC or at future high…
Using a quite accurate flavour-independence of $nS$-level mass differences in heavy quarkonia and a corresponding quasiclassical expression for the heavy quark binding energy, one shows that experimental data on masses of mesons with heavy…
Axions, grand unification, and string theory are each compelling extensions of the Standard Model. We show that combining these frameworks imposes strong constraints on the QCD axion mass. Using unitarity arguments and explicit string…
Using the current precision electroweak data, we look for the minimal particle content which is necessary to add to the standard model in order to have a complete unification of gauge couplings and gravity at the weakly coupled heterotic…
Low-scale string models are phenomenological models in String Theory, in which the string scale M_s is of the order of TeV. String excited states which are characteristic modes in low-scale string models can be observed as resonances in…
Standard lore asserts that quantum effects generically forbid the occurrence of light (non-pseudo-Goldstone) scalars having masses smaller than the Kaluza Klein scale, M_KK, in extra-dimensional models, or the gravitino mass, M_3/2, in…
The ultrahigh energy range of neutrino physics (above $\sim 10^{7} \, \mathrm{GeV}$), as yet devoid of detections, is an open landscape with challenges to be met and discoveries to be made. Neutrino-nucleon cross sections in that range -…
We discuss the sensitivity of the processes e+e- to b b(bar), e+e- to t t(bar) and gamma gamma to H to certain residual New Physics interactions affecting the heavy quark and Higgs boson sector. With a linear collider of 500 GeV, one should…
Supersymmetric particles at the multi-TeV scale will escape direct detection at planned future colliders. However, such particles induce non-decoupling corrections in processes involving the accessible superparticles through violations of…
Four-top production and top pair production in association with missing energy at e+e- colliders are sensitive probes of beyond-the-Standard-Model physics. We consider Standard Model (SM) extensions containing a new U(1)' which couples…
The Higgs quartic coupling has now been indirectly measured at the electroweak scale. Assuming no new low-scale physics, its running is known and, together with gauge and Yukawa couplings, it is a crucial new piece of information…
We consider an extra dimensional model where the quadratically divergent top loop contribution to the Higgs mass is cancelled by an uncolored heavy "top quirk" charged under a different SU(3) gauge group. The cancellation is enforced by…
Preliminary results of the search for a Standard Model like Higgs boson at the LHC with 5 fb-1 data have just been presented by the ATLAS and CMS collaborations and an excess of events at a mass of ~125 GeV has been reported. If this excess…
Supersymmetry is one of the best motivated possibilities for new physics at the TeV scale. However, both concrete string constructions and phenomenological considerations suggest the possibility that the physics at the TeV scale could be…
We study quark and lepton mass matrix textures in a model containing an additional $U(1)_X$ gauge symmetry with origins in string compactification. The $U(1)_X$ symmetry is broken near the string scale, and we assume that the anomalies are…
A number of numerical simulations of lattice gauge theory have indicated a low mass of strange quark in 100 MeV range at the scale of $\mu=2$ GeV. In the unquenched case, which is improved over the simulation in the quenched approximation…
A search for stable and long-lived massive particles of electric charge |Q/e| = 1 or 2/3, pair-produced in e+e- collisions at centre-of-mass energies from 130 to 183 GeV, is reported by the OPAL collaboration at LEP. No evidence for…
We consider the universal extra dimensions scenario of Appelquist, Cheng, and Dobrescu, in which all of the SM fields propagate into one extra compact dimension, estimated therein to be as large as $\sim (350$ GeV$)^{-1}$. Tree-level KK…
We discuss a set of precision observables that can probe the existence of a light particle $X$ coupled to electrons in the mass range of 1-100 MeV. As a case study, we consider the recent excess of $e^+e^-$ final-state events at $\sqrt{s} =…
String theory suggests the existence of a minimum length scale. An exciting quantum mechanical implication of this feature is a modification of the uncertainty principle. In contrast to the conventional approach, this generalised…