Heavy Flavour Working Group Summary

We review theoretical and phenomenological aspects of heavy flavour production as discussed in the heavy flavour working group of the DIS 2012. Recent theoretical progress includes approximate NNLO calculations for heavy quark structure functions in deep inelastic scattering, the extension of the ACOT heavy flavour scheme to jet production, and advances in top physics where the highlight is clearly the first complete NNLO QCD prediction for top pair production in the $q \bar{q}$ annihilation channel. Furthermore, state of the art phenomenological predictions for open charm and bottom, charmonium, and single top and top pair production are discussed in addition to other topics such as the effect of double parton scattering on heavy quark production. New measurements on charm and beauty production presented in the heavy flavor working group are summarized and discussed in comparison with QCD predictions. Top quark strong and weak couplings as well as top quark properties are being measured with precision at the LHC and the Tevatron. We summarize also recent results on spectroscopy of charmonia, bottomonia and $b$-hadrons, along with studies of their decays and properties. Searches for physics beyond Standard Model through precise measurements of rare decays of heavy flavours are discussed as well.Comment: 16 pages, 5 figures, to be published in the Proceedings of the XX International Workshop on Deep Inelastic Scattering, University of Bonn, 26-30th March 201

Characterizing New Physics with Polarized Beams at High-Energy Hadron Colliders

The TeV energy region is currently being explored by both the ATLAS and CMS experiments of the Large Hadron Collider and phenomena beyond the Standard Model are extensively searched for. Large fractions of the parameter space of many models have already been excluded, and the ranges covered by the searches will certainly be increased by the upcoming energy and luminosity upgrades. If new physics has to be discovered in the forthcoming years, the ultimate goal of the high-energy physics program will consist of fully characterizing the newly-discovered degrees of freedom in terms of properties such as their masses, spins and couplings. The scope of this paper is to show how the availability of polarized beams at high-energy proton-proton colliders could yield a unique discriminating power between different beyond the Standard Model scenarios. We first discuss in a model-independent way how this discriminating power arises from the differences between polarized and unpolarized parton distribution functions. We then demonstrate how polarized beams allow one not only to disentangle different production mechanisms giving the same final-state signature, but also to obtain information on the parameters of the hypothetical new physics sector of the theory. This is illustrated in the case of a particular class of scenarios leading to monotop production. We consider three specific models that could produce a monotop signature in unpolarized proton collisions, and show how they could be distinguished by means of single- and double-spin asymmetries in polarized collisions. Our results are presented for both the Large Hadron Collider operating at a center-of-mass energy of 14 TeV and a recently proposed Future Circular Collider assumed to collide protons at a center-of-mass energy of 100 TeV.Comment: 23 pages, 12 figures, 1 table; version accepted by JHE

PyR@TE: Renormalization Group Equations for General Gauge Theories

Although the two-loop renormalization group equations for a general gauge field theory have been known for quite some time, deriving them for specific models has often been difficult in practice. This is mainly due to the fact that, albeit straightforward, the involved calculations are quite long, tedious and prone to error. The present work is an attempt to facilitate the practical use of the renormalization group equations in model building. To that end, we have developed two completely independent sets of programs written in Python and Mathematica, respectively. The Mathematica scripts will be part of an upcoming release of SARAH 4. The present article describes the collection of Python routines that we dubbed PyR@TE which is an acronym for "Python Renormalization group equations At Two-loop for Everyone". In PyR@TE, once the user specifies the gauge group and the particle content of the model, the routines automatically generate the full two-loop renormalization group equations for all (dimensionless and dimensionful) parameters. The results can optionally be exported to Latex and Mathematica, or stored in a Python data structure for further processing by other programs. For ease of use, we have implemented an interactive mode for PyR@TE in form of an IPython Notebook. As a first application, we have generated with PyR@TE the renormalization group equations for several non-supersymmetric extensions of the Standard Model and found some discrepancies with the existing literature.Comment: 33 page

Frontiers of QCD with Precision nPDFs

Searches for new physics will increasingly depend on identifying deviations from precision Standard Model (SM) predictions. Quantum Chromodynamics (QCD) will necessarily play a central role in this endeavor as it provides the framework for the parton model. However, as we move to higher orders and into extreme kinematic regions, we begin to see the full complexities of the QCD theory. Recent theoretical developments improve our ability to analyze both proton and nuclear PDFs across the full kinematic range. These developments are incorporated into the new nCTEQ15 PDFs, and we review these developments with respect to future measurements, and identify areas where additional effort is required.Comment: Published in the "6th International conference on Physics Opportunities at Electron-Ion colliders (POETIC6)

NLO+NLL limits on W′W' and Z′Z' gauge boson masses

QCD resummation predictions for the production of new charged ($W'$) and neutral ($Z'$) heavy gauge bosons decaying leptonically are presented. These results are obtained with our resummation code at next-to-leading order and next-to-leading logarithmic (NLO+NLL) accuracy. Our predictions are compared to PYTHIA at leading order (LO) supplemented with parton showers (PS) and FEWZ at NLO and next-to-next-to-leading order (NNLO) for the $p_T$-differential and total cross sections in the Sequential Standard Model (SSM) and general SU(2)$\times$SU(2)$\times$U(1) models. We show that the importance of resummation for total cross sections increases with the gauge boson mass. Finally, the latest ATLAS and CMS results are reinterpreted to derive new limits at NLO+NLL on $W'$ and $Z'$ boson masses in general extensions of the Standard Model.Comment: Proceeding of the XXIII International Workshop on Deep Inelastic Scattering and Related Subjects, April 27 - May 1, 2015, Southern Methodist University, Dallas, Texa

The general Two-Higgs Doublet Model in a gauge-invariant form

In the general Two-Higgs Doublet Model it has been shown that the Higgs potential can be expressed in terms of gauge-independent quantities. In particular, stability, electroweak symmetry breaking, and CP symmetry can be understood in a concise way, avoiding unphysical gauge degrees of freedom. We complete this program and show how all the masses, the trilinear and quartic scalar interactions, the gauge-boson-Higgs interactions, as well as the Yukawa couplings in the general THDM can be expressed in a gauge-invariant way.Comment: 40 page

On the intrinsic bottom content of the nucleon and its impact on heavy new physics at the LHC

Heavy quark parton distribution functions (PDFs) play an important role in several Standard Model and New Physics processes. Most analyses rely on the assumption that the charm and bottom PDFs are generated perturbatively by gluon splitting and do not involve any non-perturbative degrees of freedom. It is clearly necessary to test this hypothesis with suitable QCD processes. Conversely, a non-perturbative, intrinsic heavy quark parton distribution has been predicted in the literature. We demonstrate that to a very good approximation the scale-evolution of the intrinsic heavy quark content of the nucleon is governed by non-singlet evolution equations. This allows us to analyze the intrinsic heavy quark distributions without having to resort to a full-fledged global analysis of parton distribution functions. We exploit this freedom to model intrinsic bottom distributions which are so far missing in the literature in order to estimate the impact of this non-perturbative contribution to the bottom-quark PDF, and on parton--parton luminosities at the LHC. This technique can be applied to the case of intrinsic charm, albeit within the limitations outlined in the following.Comment: 23 pages, 11 figure

Open charm hadroproduction and the charm content of the proton

We advocate charmed-hadron inclusive hadroproduction as a laboratory to probe intrinsic charm (IC) inside the colliding hadrons. Working at next-to-leading order in the general-mass variable-flavor-number scheme endowed with non-perturbative fragmentation functions recently extracted from a global fit to e^+e^- annihilation data from KEKB, CESR, and LEP1, we first assess the sensitivity of Tevatron data of D^0, D^+, and D^{*+} inclusive production to the IC parameterizations provided by Pumplin et al. We then argue that similar data from pp collisions at RHIC would have the potential to discriminate between different IC models provided they reach out to sufficiently large values of transverse momentum.Comment: 22 pages, 7 figures; discussion of large-p_T range at the Tevatron and high-energy mode of RHIC included, 2 figures added; accepted for publication in Phys. Rev.

Electroweak tt‾\overline{t} hadroproduction in the presence of heavy Z′ and W′ bosons at NLO QCD in POWHEG

We present a new calculation of next-to-leading order QCD corrections to electroweak top-quark pair hadroproduction in extensions of the Standard Model (SM) with extra heavy neutral and charged spin-1 resonances which considerably extends and improves an earlier calculation performed by some of us. In particular, we allow for flavor-non-diagonal Z′ couplings and take into account nonresonant production in the SM and beyond including the contributions with $\overline{t}$-channel W and W′ bosons. As a result, models with a more complicated flavor structure which have been proposed to explain the flavor anomalies in B decays can now be accommodated in our code. Moreover, the new $\overline{t}$-channel contributions lead to improved cross sections predictions at higher energies beyond the LHC reach. All amplitudes are generated using the recola2 package. As in our previous work, we include next-to-leading order QCD corrections and consistently match to parton showers with the POWHEG method fully taking into account the interference effects between the SM and new physics amplitudes. We consider the sequential Standard Model, the topcolor model, as well as the third family hypercharge model featuring non-flavor-diagonal Z′ couplings and present numerical results for t$\overline{t}$ cross sections at hadron colliders with a center-of-mass energy up to 100 TeV