Related papers: Comments on the high-$Q^2$ HERA anomaly
The H1 Collaboration at the DESY electron-proton collider HERA has observed, in photoproduction and neutral-current deep-inelastic scattering, an unexpected excess of events with isolated leptons and missing transverse momentum, especially…
The four fermion contact interactions, required to explain the anomalous HERA result, could come from the exchange of new heavy (probably composite) resonances. Depending on their charges and quantum numbers, one gets different scenarios…
We study the sensitivity of HERA to new physics using the helicity suppressed reaction $e_R p \rightarrow \nu X $, where the final neutrino can be a standard model one or a heavy neutrino. The approach is model independent and is based on…
In the hadroproduction of charm (or heavy flavours in general) in the context of string fragmentation, the pull of a beam remnant at the other end of a string may give a charm hadron more energy than the perturbatively produced one. The…
We present theoretical and experimental considerations pertaining to deeply inelastic heavy-flavour production at HERA. The various theoretical uncertainties in the cross section calculation are discussed. Cuts are imposed to determine the…
The existing anomalies appearing in decays of the form $b\to s \ell^+ \ell^-$ constitute a possible hint for new physics. We point out that modifications to the SM results due to heavy neutrinos could account for the observed deviations…
Leptoquarks are hypothetical new particles, which couple quarks directly to leptons. They experienced a renaissance in recent years as they are prime candidates to explain the so-called \textit{flavor anomalies}, i.e. the deviations between…
HERA is the only high energy electron-proton collider in the world today and hence has unique opportunities both to probe the structure of the proton and to search for physics beyond the Standard Model. Results are presented for…
We propose a new relation between quark mixing matrix and lepton mixing matrix. Since the parameters in the quark sector are well determined, we employ them to describe the mixing of leptons. Phenomenologically, we study the neutrino…
The cross section for production of R-parity violating squarks ($\tilde{q}$) or leptoquarks ($LQ$) with masses above 200 GeV by positron-proton scattering at HERA can be substantially increased by a moderate increase of the beam energies.…
The recently reported excess of events at HERA compared to QCD calculations impels us to examine all possible Standard Model explanations before invoking ``new physics''. We explore the possibility of adding an unusual, but small, component…
If the LHC should fail to observe direct signals for new physics, it may become necessary to look for new physics effects in rare events such as flavour-changing decays of the top quark, which, in the Standard Model, are predicted to be too…
The effects of Scalar Leptoquarks in various channels have been analysed for the HERA collider and also for an eventual new $ep$ machine running at higher energies. We emphasize the relevance of polarized beams.
Events with an isolated high $p_T$ lepton, a hadron jet and missing energy as observed in the H1 experiment at HERA, are potentially associated with R-parity violation in supersymmetric theories. However, stringent kinematic constraints…
Multi-electron and multi-muon production at high transverse momentum is measured in $ep$ scattering at HERA. Previous published analyses are extended, combining new HERA II data taken in 2003-2004 with previous HERA I data sample. In…
The prospects of physics beyond the standard model in deep inelastic scattering are reviewed, emphasizing the search for contact interactions, for leptoquarks and for supersymmetry with R-parity violation. R-parity violating supersymmetry…
Multiple interaction models satisfying $s$-channel unitarity predict that, in contrast to inelastic processes, factorization is violated in diffractive processes. The size of this effect can be characterized in terms of the rapidity gap…
Measurements of heavy quark production, particularly from HERA, their theoretical understanding and their relevance for the LHC are reviewed. The status of beauty and charm production is discussed in the context of the different components…
Processes commonly studied at the Large Hadron Collider (LHC) are induced by quarks and gluons inside the protons of the LHC beams. In this letter we demonstrate that, since protons also contain leptons, it is possible to target…
Perturbative QCD in the high-energy limit describes the evolution of scattering amplitudes with increasing energy towards and into the so-called saturation regime. Comparisons of the predictions with experimental data for a number of…