Search

VBFNLO is a flexible parton level Monte Carlo program for the simulation of vector boson fusion (VBF), QCD-induced single and double vector boson production plus two jets, and double and triple vector boson production (plus jet) in hadronic collisions at next-to-leading order (NLO) in the strong coupling constant, as well as Higgs boson plus two and three jet production via gluon fusion at the one-loop level. For the new version -- Version 3.0 -- several major enhancements have been included. An interface according to the Binoth Les Houches Accord (BLHA) has been added for all VBF and di/tri-boson processes including fully leptonic decays. For all dimension-8 operators affecting vector boson scattering (VBS) processes, a modified T-matrix unitarization procedure has been implemented. Several new production processes have been added, namely the VBS $Z\gamma jj$ and $\gamma \gamma jj$ processes at NLO, $\gamma \gamma jj $, $WWj$ and $ZZj$ production at NLO including the loop-induced gluon-fusion contributions and the gluon-fusion one-loop induced $\Phi jjj$ ($\Phi$ is a CP-even or CP-odd scalar boson) process at LO, retaining the full top-mass dependence. Finally, the code has been parallelized using OpenMPI., Comment: 16 pages, 3 figures; new code available at http://ific.uv.es/vbfnlo/. arXiv admin note: text overlap with arXiv:1107.4038

We discuss a novel approach to quantum information processing with molecules based on molecular degrees of freedom which are isolated from the environment as well as from the rest of the molecule. Such a degree of freedom can provide long-term quantum storage even in a noisy environment, and provides an independent protected quantum memory while quantum operations are performed between the rest of the molecule and external systems. We present several possibilities for realizing a quasi-hidden degree of freedom in a molecule, and discuss a number of examples for using such a degree of freedom in practice. Using quasi-hidden degrees of freedom could substantially improve the prospects for a molecule-based quantum computer.

Non-radiative energy transfer between a Rydberg atom and a polar molecule can be controlled by a DC electric field. Here we show how to exploit this control for state-resolved, non-destructive detection and spectroscopy of the molecules where the lineshape reflects the type of molecular transition. Using the example of ammonia, we identify the conditions for collision-mediated spectroscopy in terms of the required electric field strengths, relative velocities, and molecular densities. Rydberg atom-enabled spectroscopy is feasible with current experimental technology, providing a versatile detection method as basic building block for applications of polar molecules in quantum technologies and chemical reaction studies., Comment: 10 pages, 7 figures

Reaching high densities is a key step towards cold-collision experiments with polyatomic molecules. We use a cryofuge to load up to 2$\times10^7$ CH$_3$F molecules into a box-like electric trap, achieving densities up to 10$^7$/cm$^3$ at temperatures around 350 mK where the elastic dipolar cross-section exceeds 7$\times$10$^{-12}$cm$^2$. We measure inelastic rate constants below 4$\times$10$^{-8}$cm$^3$/s and control these by tuning a homogeneous electric field that covers a large fraction of the trap volume. Comparison to ab-initio calculations gives excellent agreement with dipolar relaxation. Our techniques and findings are generic and immediately relevant for other cold-molecule collision experiments., Comment: To be published in Physical Review Letters: https://journals.aps.org/prl/accepted/e5070Y42Cf013066f8871d5761f80f99fa8136ff5

Rapid progress in cooling and trapping of molecules has enabled first experiments on high resolution spectroscopy of trapped diatomic molecules, promising unprecedented precision. Extending this work to polyatomic molecules provides unique opportunities due to more complex geometries and additional internal degrees of freedom. Here, this is achieved by combining a homogeneous-field microstructured electric trap, rotational transitions with minimal Stark broadening at a 'magic' offset electric field, and optoelectrical Sisyphus cooling of molecules to the low millikelvin temperature regime. We thereby reduce Stark broadening on the $J=5\leftarrow4$ ($K=3$) transition of formaldehyde at $364\,$GHz to well below $1\,$kHz, observe Doppler-limited linewidths down to $3.8\,$kHz, and determine the 'magic'-field line position with an uncertainty below $100\,$Hz. Our approach opens a multitude of possibilities for investigating diverse polyatomic molecule species.

Effective field theories (EFT) are commonly used to parameterize effects of BSM physics in vector boson scattering (VBS). For Wilson coefficients which are large enough to produce presently observable effects, the validity range of the EFT represents only a fraction of the energy range covered by the LHC, however. In order to shed light on possible extrapolations into the high energy region, a class of UV-complete toy models, with extra SU(2) multiplets of scalars or of fermions with vector-like weak couplings, is considered. By calculating the Wilson coefficients up to energy-dimension eight, and full one-loop contributions to VBS due to the heavy multiplets, the EFT approach, with and without unitarization at high energy, is compared to the perturbative prediction. For high multiplicities, e.g. nonets of fermions, the toy models predict sizable effects in transversely polarized VBS, but only outside the validity range of the EFT. At lower energies, dimension-eight operators are needed for an adequate description of the models, providing another example that dimension-eight can be more important than dimension-six operators. A simplified VBFNLO implementation is used to estimate sensitivity of VBS to such BSM effects at the LHC. Unitarization captures qualitative features of the toy models at high energy but significantly underestimates signal cross sections in the threshold region of the new particles., Comment: 39 pages, 13 figures

We present a compact \textit{in-situ} electromagnet with an active cooling system for the use in ultra-high vacuum environments. The active cooling enhances the thermal stability and increases the electric current that can be applied through the coil, promoting the generation of homogeneous magnetic fields, required for applications in real-time deposition experiments. The electromagnet has been integrated into a reflectance difference magneto-optic Kerr effect (RD-MOKE) spectroscopy system that allows the synchronous measurement of the optical anisotropy and the magneto-optic response in polar MOKE geometry. Proof of principle studies have been performed in real-time during the deposition of ultra-thin Ni films on Cu(110)-(2$\times$1)O surfaces, corroborating the extremely sharp spin reorientation transition above a critical coverage of 9 monolayers and demonstrating the potential of the applied setup for real-time and \textit{in-situ} investigations of magnetic thin films and interfaces., Comment: 7 pages, 7 figures

Cryogenic buffer gas cells have been a workhorse for the cooling of molecules in the last decades. The straightforward sympathetic cooling principle makes them applicable to a huge variety of different species. Notwithstanding this success, detailed simulations of buffer gas cells are rare, and have never been compared to experimental data in the regime of low to intermediate buffer gas densities. Here, we present a numerical approach based on a trajectory analysis, with molecules performing a random walk in the cell due to collisions with a homogeneous buffer gas. This method can reproduce experimental flux and velocity distributions of molecules emerging from the buffer gas cell for varying buffer gas densities. This includes the strong decrease in molecule output from the cell for increasing buffer gas density and the so-called boosting effect, when molecules are accelerated by buffer-gas atoms after leaving the cell. The simulations provide various insights which could substantially improve buffer-gas cell design.

The successful operation of the Large Hadron Collider (LHC) and the excellent performance of the ATLAS, CMS, LHCb and ALICE detectors in Run-1 and Run-2 with $pp$ collisions at center-of-mass energies of 7, 8 and 13 TeV as well as the giant leap in precision calculations and modeling of fundamental interactions at hadron colliders have allowed an extraordinary breadth of physics studies including precision measurements of a variety physics processes. The LHC results have so far confirmed the validity of the Standard Model of particle physics up to unprecedented energy scales and with great precision in the sectors of strong and electroweak interactions as well as flavour physics, for instance in top quark physics. The upgrade of the LHC to a High Luminosity phase (HL-LHC) at 14 TeV center-of-mass energy with 3 ab$^{-1}$ of integrated luminosity will probe the Standard Model with even greater precision and will extend the sensitivity to possible anomalies in the Standard Model, thanks to a ten-fold larger data set, upgraded detectors and expected improvements in the theoretical understanding. This document summarises the physics reach of the HL-LHC in the realm of strong and electroweak interactions and top quark physics, and provides a glimpse of the potential of a possible further upgrade of the LHC to a 27 TeV $pp$ collider, the High-Energy LHC (HE-LHC), assumed to accumulate an integrated luminosity of 15 ab$^{-1}$., Comment: Report from Working Group 1 on the Physics of the HL-LHC, and Perspectives at the HE-LHC

The bottom-up fabrication graphene nanoribbons (GNRs) has opened new opportunities to specifically control their electronic and optical properties by precisely controlling their atomic structure. Here, we address excitations in GNRs with periodic structural wiggles, so-called Chevron GNRs. Based on reflectance difference and high-resolution electron energy loss spectroscopies together with ab-initio simulations, we demonstrate that their excited-state properties are dominated by strongly bound excitons. The spectral fingerprints corresponding to different reaction stages in their bottom-up fabrication are also unequivocally identified, allowing us to follow the exciton build-up from the starting monomer precursor to the final ribbon structure.

We perform a comprehensive investigation of F\"orster resonant energy transfer in a room-temperature thermal mixture of ammonia molecules and rubidium Rydberg atoms. Fully state-resolved measurement of the Rydberg-atom populations is achieved by combining millimeter-wave state transfer with state-selective field ionization. This allows aspects of the energy transfer process such as state dependence, ammonia pressure dependence, and dependence on the energy resonance condition to be investigated in detail. Our results pave the way for future quantum experiments combining polar molecules and Rydberg atoms.

We present precision spectroscopy on electrically trapped formaldehyde (H$_2$CO), demonstrating key attributes which will enable molecular spectroscopy with unprecedented precision. Our method makes use of a microstructured electric trap with homogeneous fields in the trap center and rotational transitions with minimal Stark broadening at a 'magic' offset electric field. Using molecules cooled to the low millikelvin temperature regime via optoelectrical Sisyphus cooling, we reduce Stark broadening on the $J=5\leftarrow4$ ($K=3$) transition at 364 GHz to well below 1 kHz, observe Doppler-limited linewidths down to 3.8 kHz, and determine the line position with sub-kHz uncertainty. Our results and clear prospects for even narrower spectra pave the way towards in-trap precision spectroscopy on diverse molecule species.

Weak vector boson scattering (VBS) at the LHC provides an excellent source of information on the structure of quartic gauge couplings and possible effects of physics beyond the SM in electroweak symmetry breaking. Parameterizing deviations from the SM within an effective field theory at tree level, the dimension-8 operators, which are needed for sufficiently general modeling, lead to unphysical enhancements of cross sections within the accessible energy range of the LHC. Preservation of unitarity limits is needed for phenomenological studies of the $VVjj$ events which signify VBS. Here we develop a numerical unitarization scheme for the full off-shell VBS processes and apply it to same-sign $W$ scattering, i.e. processes like $qq\to qqW^+W^+$. The scheme is implemented within the Monte Carlo program VBFNLO, including leptonic decay of the weak bosons and NLO QCD corrections. Distributions differentiating between higher dimensional operators are discussed., Comment: 24 pages, 7 figures

Rotors are functional reentry sources identified in clinically relevant cardiac arrhythmias, such as ventricular and atrial fibrillation. Ablation targeting rotor sites has resulted in arrhythmia termination. Recent clinical, experimental and modelling studies demonstrate that rotors are often anchored around fibrotic scars or regions with increased fibrosis. However the mechanisms leading to abundance of rotors at these locations are not clear. The current study explores the hypothesis whether fibrotic scars just serve as anchoring sites for the rotors or whether there are other active processes which drive the rotors to these fibrotic regions. Rotors were induced at different distances from fibrotic scars of various sizes and degree of fibrosis. Simulations were performed in a 2D model of human ventricular tissue and in a patient-specific model of the left ventricle of a patient with remote myocardial infarction. In both the 2D and the patient-specific model we found that without fibrotic scars, the rotors were stable at the site of their initiation. However, in the presence of a scar, rotors were eventually dynamically anchored from large distances by the fibrotic scar via a process of dynamical reorganization of the excitation pattern. This process coalesces with a change from polymorphic to monomorphic ventricular tachycardia., Comment: 16 pages, 7 figures

Vector-boson scattering processes are of great importance for the current run-II and future runs of the Large Hadron Collider. The presence of triple and quartic gauge couplings in the process gives access to the gauge sector of the Standard Model (SM) and possible new-physics contributions there. To test any new-physics hypothesis, sound knowledge of the SM contributions is necessary, with a precision which at least matches the experimental uncertainties of existing and forthcoming measurements. In this article we present a detailed study of the vector-boson scattering process with two positively-charged leptons and missing transverse momentum in the final state. In particular, we first carry out a systematic comparison of the various approximations that are usually performed for this kind of process against the complete calculation, at LO and NLO QCD accuracy. Such a study is performed both in the usual fiducial region used by experimental collaborations and in a more inclusive phase space, where the differences among the various approximations lead to more sizeable effects. Afterwards, we turn to predictions matched to parton showers, at LO and NLO: we show that on the one hand, the inclusion of NLO QCD corrections leads to more stable predictions, but on the other hand the details of the matching and of the parton-shower programs cause differences which are considerably larger than those observed at fixed order, even in the experimental fiducial region. We conclude with recommendations for experimental studies of vector-boson scattering processes., Comment: Data and input files are available at: https://github.com/VBSCanAction/VBSComparison/ . 28 pages including figures and references. Matches the journal version

This document summarises the talks and discussions happened during the VBSCan Split17 workshop, the first general meeting of the VBSCan COST Action network. This collaboration is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders., Comment: 41 pages including references, 11 figures, summary of the talks and discussions happened during the first VBSCan workshop: https://indico.cern.ch/event/629638/. Note that in v2 the original title "VBSCan Split 2017 Workshop Summary" has been modified according to the published version

Ultracold molecules represent a fascinating research frontier in physics and chemistry, but it has proven challenging to prepare dense samples at low velocities. Here we present a solution to this goal by a non-conventional approach dubbed cryofuge. It employs centrifugal force to bring cryogenically cooled molecules to kinetic energies below $1\,$K$\times k_B$ in the laboratory frame, with corresponding fluxes exceeding $10^{10}$/s at velocities below $20\,$m/s. By attaining densities higher than $10^9$/cm$^3$ and interaction times longer than $25\,$ms in samples of fluoromethane as well as deuterated ammonia, we observe cold dipolar collisions between molecules and determine their collision cross sections., Comment: 4 pages, 4 figures

Vector-boson scattering (VBS) processes provide particularly promising means for probing the mechanism of electroweak symmetry breaking and to search for new physics in the weak sector. In the environment of a future proton-proton collider operating at a center-of-mass energy of 100 TeV, unprecedented opportunities arise for the investigation of this important class of reactions. We highlight the prominent features of VBS processes in this energy regime and discuss how the VBS signal can be isolated in the presence of a priori large QCD backgrounds. We find excellent opportunities for the analysis of VBS reactions in a kinematic range that is inaccessible to present colliders., Comment: 26 pages, 14 figures; matches version published by Phys. Rev. D

Cross sections and differential distributions for ZA production in association with two jets via vector boson fusion are presented at next-to-leading order in QCD. The leptonic decays of the Z boson with full off-shell effects and spin correlations are taken into account. The uncertainties due to different scale choices and pdf sets are studied. Furthermore, we analyze the effect of including anomalous quartic gauge couplings at NLO QCD., Comment: 10 pages, 11 figures

Precise predictions for Higgs production via vector-boson fusion play an important role when testing the properties of the Higgs boson and probing new-physics effects. While the inclusive cross section changes little when including NNLO and N3LO QCD corrections, a differential NNLO calculation with typical VBF cuts shows large corrections of up to 10% in distributions. In this article, we investigate the dependence of the differential NNLO QCD calculation on the jet definition. Starting from the known results at a fixed jet clustering choice, we use the electroweak H+3 jets production cross section at NLO precision to derive NNLO results for H+2 jets production for other jet definitions. We find that larger clustering radii significantly reduce the impact of NNLO corrections. The sizable NNLO corrections for distributions are largely caused by the broader energy flow inside jets at NNLO and are to be expected generally for processes with jets at LO., Comment: 10 pages, 4 figures; v2: extended discussion of procedure, results and conclusions unchanged, version to appear in PRD

Optical frequency combs (OFC) provide a convenient reference for the frequency stabilization of continuous-wave lasers. We demonstrate a frequency control method relying on tracking over a wide range and stabilizing the beat note between the laser and the OFC. The approach combines fast frequency ramps on a millisecond timescale in the entire mode-hop free tuning range of the laser and precise stabilization to single frequencies. We apply it to a commercially available optical parametric oscillator (OPO) and demonstrate tuning over more than 60 GHz with a ramping speed up to 3 GHz/ms. Frequency ramps spanning 15 GHz are performed in less than 10 ms, with the OPO instantly relocked to the OFC after the ramp at any desired frequency. The developed control hardware and software is able to stabilize the OPO to sub-MHz precision and to perform sequences of fast frequency ramps automatically., Comment: 8 pages, 7 figures, accepted for publication in Review of Scientific Instruments

We study WZ production with anomalous couplings at $\bar{n}$NLO QCD using the LoopSim method in combination with the Monte Carlo program VBFNLO. Higher order corrections to WZ production are dominated by additional hard jet radiation. Those contributions are insensitive to anomalous couplings and should thus be removed in analyses. We do this using a dynamical jet veto based on the transverse energy of the QCD and EW final state particles. This removes jet dominated events without introducing problematic logs like a fixed $p_{\text{T}}$ jet veto., Comment: Talk presented at Fourth Annual Large Hadron Collider Physics conference (LHCP2016), 13-18 June 2016, Lund, Sweden (10 pages)

A highly sensitive, general, and preferably nondestructive technique to detect polar molecules would greatly advance a number of fields, in particular quantum science with cold and ultracold molecules. Here, we propose using resonant energy transfer between molecules and Rydberg atoms to detect molecules. Based on an energy transfer cross section of $>10^{-6}\,$cm$^2$ for sufficiently low collision energies, a near unit efficiency non-destructive detection of basically any polar molecule species in a well defined internal state should be possible.

This Report summarizes the results of the activities of the LHC Higgs Cross Section Working Group in the period 2014-2016. The main goal of the working group was to present the state-of-the-art of Higgs physics at the LHC, integrating all new results that have appeared in the last few years. The first part compiles the most up-to-date predictions of Higgs boson production cross sections and decay branching ratios, parton distribution functions, and off-shell Higgs boson production and interference effects. The second part discusses the recent progress in Higgs effective field theory predictions, followed by the third part on pseudo-observables, simplified template cross section and fiducial cross section measurements, which give the baseline framework for Higgs boson property measurements. The fourth part deals with the beyond the Standard Model predictions of various benchmark scenarios of Minimal Supersymmetric Standard Model, extended scalar sector, Next-to-Minimal Supersymmetric Standard Model and exotic Higgs boson decays. This report follows three previous working-group reports: Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002), Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002), and Handbook of LHC Higgs Cross Sections: 3. Higgs properties (CERN-2013-004). The current report serves as the baseline reference for Higgs physics in LHC Run 2 and beyond., Comment: 869 pages, 295 figures, 248 tables and 1645 citations. Working Group web page: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHXSWG

This report summarises the properties of Standard Model processes at the 100 TeV pp collider. We document the production rates and typical distributions for a number of benchmark Standard Model processes, and discuss new dynamical phenomena arising at the highest energies available at this collider. We discuss the intrinsic physics interest in the measurement of these Standard Model processes, as well as their role as backgrounds for New Physics searches., Comment: 253 pages, 198 figures. Chapter 1 of the "Physics at the FCC-hh" Report

We present a comprehensive characterization of cold molecular beams from a cryogenic buffer-gas cell, providing an insight into the physics of buffer-gas cooling. Cold molecular beams are extracted from a cryogenic cell by electrostatic guiding, which is also used to measure their velocity distribution. Molecules' rotational-state distribution is probed via radio-frequency resonant depletion spectroscopy. With the help of complete trajectory simulations, yielding the guiding efficiency for all of the thermally populated states, we are able to determine both the rotational and the translational temperature of the molecules at the output of the buffer-gas cell. This thermometry method is demonstrated for various regimes of buffer-gas cooling and beam formation as well as for molecular species of different sizes, $\rm{CH_3F}$ and $\rm{CF_3CCH}$. Comparison between the rotational and translational temperatures provides evidence of faster rotational thermalization for the $\rm{CH_3F-He}$ system in the limit of low He density. In addition, the relaxation rates for different rotational states appear to be different.

We demonstrate direct cooling of gaseous formaldehyde (H2CO) to the microkelvin regime. Our approach, optoelectrical Sisyphus cooling, provides a simple dissipative cooling method applicable to electrically trapped dipolar molecules. By reducing the temperature by three orders of magnitude and increasing the phase-space density by a factor of ~$10^4$ we generate an ensemble of $3\cdot10^5$ molecules with a temperature of about 420\mu K, populating a single rotational state with more than 80% purity.

Controlling the internal degrees of freedom is a key challenge for applications of cold and ultracold molecules. Here, we demonstrate rotational-state cooling of trapped methyl fluoride molecules (CH3F) by optically pumping the population of 16 M-sublevels in the rotational states J=3,4,5, and 6 into a single level. By combining rotational-state cooling with motional cooling, we increase the relative number of molecules in the state J=4, K=3, M=4 from a few percent to over 70%, thereby generating a translationally cold (~30mK) and nearly pure state ensemble of about 10^6 molecules. Our scheme is extendable to larger sets of initial states, other final states and a variety of molecule species, thus paving the way for internal-state control of ever larger molecules.

In these proceedings, we review results for several di-boson production processes beyond NLO QCD at high transverse momenta using the VBFNLO Monte-Carlo program together with the LOOPSIM method. Additionally, we show for the WZ production process how higher order QCD corrections can resemble anomalous coupling effects., Comment: Conference Proceedings:C15-05-25.1

Detecting the internal state of polar molecules is a substantial challenge when standard techniques such as resonance-enhanced multi photon ionization (REMPI) or laser-induced fluorescense (LIF) do not work. As this is the case for most polyatomic molecule species, we here investigate an alternative based on state selective removal of molecules from an electrically trapped ensemble. Specifically, we deplete molecules by driving rotational and/or vibrational transitions to untrapped states. Fully resolving the rotational state with this method can be a considerable challenge as the frequency differences between various transitions is easily substantially less than the Stark broadening in an electric trap. However, making use of a unique trap design providing homogeneous fields in a large fraction of the trap volume, we successfully discriminate all rotational quantum numbers, including the rotational M-substate.