Intrinsic bottom 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. On the other hand, non- perturbative, intrinsic heavy quark parton distributions have 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 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. We estimate the impact of the non-perturbative contribution to the charm and bottom-quark PDFs and on several important parton-parton luminosities at the LHC.Comment: 6 pages, proceedings of POETIC VI: 6th International conference on Physics Opportunities at Electron-Ion collider. arXiv admin note: substantial text overlap with arXiv:1507.0893

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

Ultrasonic Testing of a Nuclear Fuel Cladding Pipe, Modelization with a Hybrid Method and Experiments

Nuclear Fuel cladding pipes are long and thin tubes made of zirconium-alloy whose purpose is to confine the fissile material in a nuclear reactor. During their 3 year cycle in the reactor\u27s core they must maintain their integrity while enduring severe stresses (heat, corrosion and irradiation). Nondestructive evaluations are performed at several stages of the manufacturing process. ASTM International provides recommendations regarding the Ultrasonic Testing (UT) of zirconium cladding pipes at the end of the production line[1]. The recommended setup is a pulse-echo immersion testing at frequency higher than 5 MHz where transverse and longitudinal calibration notches are used for defining alert levels with sufficient margins. AREVA NP\u27s project is to build a numerical model of this UT in order to enhance the selectivity of the tests and reduce the cost of over-quality. This model is based on the hybridization of a semi-analytic method and a Finite Difference Time Domain (FDTD) method. They are used in conjunction with a time domain reciprocity equation which allows to back-propagate the signal from a line close to the metallic pipe as well as around a potential crack (fig. 1). Results for two positions of the back-propagation line are compared with an experimental signal recorded in a water tank (fig. 2). The flaw used in this study case is a rectangular longitudinal calibration notch. This result is the first step towards an efficient computation of received signals for many different crack positions and geometries

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

Vacuum stability and perturbativity of SU(3) scalars

We calculate the vacuum stability conditions and renormalisation group equations for the extensions of standard model with a higher colour multiplet scalar up to the representation 1 5 0 that leaves the strong interaction asymptotically free. In order to find the vacuum stability conditions, we calculate the orbit spaces for the self-couplings of the higher multiplets, which for the representations 1 5 and 1 5 0 of SU(3)(c) are highly complicated. However, if the scalar potential is linear in orbit space variables, it is sufficient to know the convex hull of the orbit space. Knowledge of the orbit spaces also facilitates the minimisation of the potentials. In contrast to the self-couplings of other multiplets, we find that the scalar quartic couplings of the representations 3 and 8 walk rather than run, remaining nearly constant and perturbative over a vast energy range. We describe the conditions for walking couplings using a schematic model. With these technical results at hand we revise earlier results of generation of new scales with large SU(3) c scalar multiplets. Our results are easily extendable to models of new physics with additional SU(3) or SU(N) gauge symmetries.Peer reviewe

A precision study of the fine tuning in the DiracNMSSM

Recently the DiracNMSSM has been proposed as a possible solution to reduce the fine tuning in supersymmetry. We determine the degree of fine tuning needed in the DiracNMSSM with and without non-universal gaugino masses and compare it with the fine tuning in the GNMSSM. To apply reasonable cuts on the allowed parameter regions we perform a precise calculation of the Higgs mass. In addition, we include the limits from direct SUSY searches and dark matter abundance. We find that both models are comparable in terms of fine tuning, with the minimal fine tuning in the GNMSSM slightly smaller.Comment: 20 pages + appendices, 10 figure