arXiv subjects

Martin Jung

Publications and source records attributed to Martin Jung.

At least 37 records · Page 2Linked to original sources

arXiv2018

The FLUXCOM ensemble of global land-atmosphere energy fluxes

Although a key driver of Earth's climate system, global land-atmosphere energy fluxes are poorly constrained. Here we use machine learning to merge energy flux measurements from FLUXNET eddy covariance towers with remote sensing and meteorological data to estimate net radiation, latent and sensible heat and their uncertainties. The resulting FLUXCOM database comprises 147 global gridded products in two setups: (1) 0.0833$°$ resolution using MODIS remote sensing data (RS) and (2) 0.5$°$ resolution using remote sensing and meteorological data (RS+METEO). Within each setup we use a full factorial design across machine learning methods, forcing datasets and energy balance closure corrections. For RS and RS+METEO setups respectively, we estimate 2001-2013 global (${\pm}$ 1 standard deviation) net radiation as 75.8${\pm}$1.4 ${W\ m^{-2}}$ and 77.6${\pm}$2 ${W\ m^{-2}}$, sensible heat as 33${\pm}$4 ${W\ m^{-2}}$ and 36${\pm}$5 ${W\ m^{-2}}$, and evapotranspiration as 75.6${\pm}$10 ${\times}$ 10$^3$ ${km^3\ yr^{-1}}$ and 76${\pm}$6 ${\times}$ 10$^3$ ${km^3\ yr^{-1}}$. FLUXCOM products are suitable to quantify global land-atmosphere interactions and benchmark land surface model simulations.

physics.ao-ph↗

arXiv2018

Flight Gate Assignment with a Quantum Annealer

Optimal flight gate assignment is a highly relevant optimization problem from airport management. Among others, an important goal is the minimization of the total transit time of the passengers. The corresponding objective function is quadratic in the binary decision variables encoding the flight-to-gate assignment. Hence, it is a quadratic assignment problem being hard to solve in general. In this work we investigate the solvability of this problem with a D-Wave quantum annealer. These machines are optimizers for quadratic unconstrained optimization problems (QUBO). Therefore the flight gate assignment problem seems to be well suited for these machines. We use real world data from a mid-sized German airport as well as simulation based data to extract typical instances small enough to be amenable to the D-Wave machine. In order to mitigate precision problems, we employ bin packing on the passenger numbers to reduce the precision requirements of the extracted instances. We find that, for the instances we investigated, the bin packing has little effect on the solution quality. Hence, we were able to solve small problem instances extracted from real data with the D-Wave 2000Q quantum annealer.

quant-ph↗

arXiv2018

Analytic inclusion of the scale dependence of the anomalous dimension matrix in Standard Model Effective Theory

The renormalization group equations (RGEs) in Standard Model effective theory are usually either solved analytically, neglecting the scale dependence of gauge and Yukawa couplings, or numerically without such approximations. We present analytic solutions of RGEs that take into account the dominant scale dependence of the anomalous-dimension matrix due to the running of the QCD coupling and of the top-Yukawa coupling. We consider first the case for which a given operator is generated directly through mixing with the parent operator whose Wilson coefficient is non-vanishing at the new physics scale. Subsequently we consider the case of two-step running, in which two operators do not mix directly, but only via a third mediator operator. We generalize these solutions to an arbitrary number of operators and show how even in this case analytic solutions can be obtained.

hep-ph↗

arXiv2018

Model-independent determinations of the electron EDM and the role of diamagnetic atoms

We perform model-independent analyses extracting limits for the electric dipole moment of the electron and the P,T-odd scalar-pseudoscalar (S-PS) nucleon-electron coupling from the most recent measurements with atoms and molecules. The analysis using paramagnetic systems, only, is improved substantially by the inclusion of the recent measurement on HfF+ ions, but complicated by the fact that the corresponding constraints are largely aligned, owing to a general relation between the coefficients for the two contributions. Since this same relation does not hold in diamagnetic systems, it is possible to find atoms that provide essentially orthogonal constraints to those from para\-magnetic ones. However, the coefficients are suppressed in closed-shell systems and enhancements of P,T-odd effects are only prevalent in the presence of hyperfine interactions. We formulate the hyperfine-induced time-reversal-symmetry breaking S-PS nucleon-electron interaction in general atoms in a mixed perturbative and variational approach, based on electronic Dirac-wavefunctions including the effects of electron correlations. The method is applied to the Hg atom, yielding the first direct calculation of the coefficient of the S-PS nucleon-electron coupling in a diamagnetic system. This results in additionally improved model-independent limits for both the electron EDM and the nucleon-electron coupling from the global fit. Finally we employ this fit to provide indirect limits for several paramagnetic systems under investigation.

hep-ph↗

arXiv2017

Yukawa enhancement of $Z$-mediated New Physics in $ΔS = 2$ and $ΔB = 2$ Processes

We discuss Yukawa-enhanced contributions from $Z$-mediated new physics to down-type quark $ΔF=2$ processes in the framework of the standard model gauge-invariant effective theory (SMEFT). Besides the renormalization group (RG) mixing of the $Z$-mediating $ψ^2 H^2 D$ operators into $ΔF = 2$ operators, we include at the electroweak scale one-loop (NLO) matching corrections consistently, necessary for the removal of the matching scale dependence. We point out that the right-handed $Z$-mediated interactions generate through Yukawa RG mixing $ΔF=2$ left-right operators, which are further enhanced through QCD RG effects and chirally enhanced hadronic matrix elements. We investigate the impact of these new effects on the known correlations between $ΔF=2$ and $ΔF=1$ transitions in the SMEFT framework and point out qualitative differences to previous parameterizations of $Z$-mediated new physics that arise for the left-handed case. We illustrate how specific models fit into our model-independent framework by using four models with vector-like quarks. We carry out model-independent analyses of scenarios with purely left-handed and purely right-handed new-physics $Z$ couplings for each of the three sectors $s\to d$, $b\to s$ and $b\to d$. Specifically we discuss the correlations between $\varepsilon'/\varepsilon$, $\varepsilon_K$, $K_L\to μ^+μ^-$ $K^+\to π^+ν\barν$ and $K_L\toπ^0ν\barν$ in the Kaon sector, and $ϕ_s$, $B_s\toμ^+μ^-$ and $B\to K^{(*)} (μ^+μ^-, ν\barν)$ in the $b\to s$ sector and $B_d\toμ^+μ^-$ in the $b\to d$ sector.

hep-ph↗

arXiv2017

Scalar contributions to $b\to c (u) τν$ transitions

We perform a comprehensive analysis of scalar contributions in $b \to c τν$ transitions including the latest measurements of $R(D^{(*)})$, the $q^2$ differential distributions in $B \to D^{(*)} τν$, the $τ$ polarization asymmetry for $B \to D^{*} τν$, and the bound derived from the total width of the $B_c$ meson. We find that scalar contributions with the simultaneous presence of both left- and right-handed couplings to quarks can explain the available data, specifically $R(D^{(*)})$ together with the measured differential distributions. However, the constraints from the total $B_c$ width present a slight tension with the current data on $B \to D^{*}τν$ in this scenario, preferring smaller values for $R(D^*)$. We discuss possibilities to disentangle scalar new physics from other new-physics scenarios like the presence of only a left-handed vector current, via additional observables in $B \to D^{(*)}τν$ decays or additional decay modes like the baryonic $Λ_b \to Λ_c τν$ and the inclusive $B \to X_c τν$ decays. We also analyze scalar contributions in $b \to u τν$ transitions, including the latest measurements of $B \to τν$, providing predictions for $Λ_b \to p τν$ and $B \to πτν$ decays. The potential complementarity between the $b \to u$ and $b \to c$ sectors is finally investigated once assumptions about the flavour structure of the underlying theory are made.

hep-ph↗

arXiv2017

Patterns of Flavour Violation in Models with Vector-Like Quarks

We study the patterns of flavour violation in renormalisable extensions of the Standard Model (SM) that contain vector-like quarks (VLQs) in a single complex representation of either the SM gauge group $G_{SM}$ or $G_{SM}' = G_{SM} \times U(1)_{L_μ- L_τ}$. We first decouple VLQs in the $M=(1-10)$ TeV range and then at the electroweak scale also $Z, Z'$ gauge bosons and additional scalars to study the resulting phenomenology that depends on the relative size of $Z$- and $Z'$-induced flavour-changing neutral currents, as well as the size of $ΔF=2$ contributions including the effects of renormalisation group Yukawa evolution from $M$ to the electroweak scale that turn out to be very important for models with right-handed currents through the generation of left-right operators. In addition to rare decays like $P\to \ell\bar\ell$, $P\to P' \ell\bar\ell$, $P\to P'ν\barν$ with $P=K, B_s, B_d$ and $ΔF=2$ observables we analyze the ratio $\varepsilon'/\varepsilon$ which appears in the SM to be significantly below the data. We study patterns and correlations between these observables which taken together should in the future allow for differentiating between VLQ models. In particular the patterns in models with left-handed and right-handed currents are markedly different from each other. Among the highlights are large $Z$-mediated new physics effects in Kaon observables in some of the models and significant effects in $B_{s,d}$-observables. $\varepsilon'/\varepsilon$ can easily be made consistent with the data, implying then uniquely the suppression of $K_L\to π^0 ν\barν$. Significant enhancements of $Br(K^+\to π^+ ν\barν)$ are still possible. We point out that the combination of $ΔF=2$ and $ΔF=1$ observables in a given meson system generally allows to determine the masses of VLQs independently of the size of VLQ couplings.

hep-ph↗

arXiv2016

Theory of electric dipole moments and lepton flavour violation

Electric dipole moments and charged-lepton flavour-violating processes are extremely sensitive probes for new physics, complementary to direct searches as well as flavour-changing processes in the quark sector. Beyond the "smoking-gun" feature of a potential significant measurement, however, it is crucial to understand their implications for new physics models quantitatively. The corresponding multi-scale problem of relating the existing high-precision measurements to fundamental parameters can be approached model-independently to a large extent; however, care must be taken to include the uncertainties from especially nuclear and QCD calculations properly.

hep-ph↗

arXiv2016

Non-universal Z' models with protected flavour-changing interactions

We define a new class of Z' models with neutral flavour-changing interactions at tree level in the down-quark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavoured U(1)' gauge symmetry, rendering these models particularly predictive. The same symmetry implies lepton-flavour non-universal couplings, fully determined by the gauge structure of the model. Our models allow to address several presently observed deviations from the SM and specific correlations among the new physics contributions to the Wilson coefficients C9,10(l) can be tested in b->sll transitions. We furthermore predict lepton-universality violations in Z' decays, testable at the LHC.

hep-ph↗

arXiv2015

Branching ratio measurements and isospin violation in B-meson decays

The approximate symmetry of the strong interactions under isospin transformations is among the most precise tools available to control hadronic matrix elements. It is crucial in extracting fundamental parameters, but also provides avenues for the search of phenomena beyond the Standard Model. The precision of the resulting predictions requires special care when determining the quantities they are to be tested with. Specifically, in the extraction of branching ratios often isospin symmetry is assumed at one point or another implicitly, implying a significant bias for precision analyses. We extract a bias-free value for the production asymmetry between charged and neutral $B$ meson pairs at $B$ factories and discuss its consequences for the determination of branching fractions generally, and isospin-violating observables like the rate asymmetries in B -> J/psi K or B -> K* gamma decays specifically.

hep-ph↗

arXiv2015

Mixing and mixing-related CP violation in the B system

We present the summary of the working group on $B$ mixing and the related CP violation at the CKM 2014 workshop. The contributions reflect the experimental and theoretical progress in the field over the last two years since the last CKM workshop.

hep-ex↗

arXiv2015

Bounds on new physics from electric dipole moments

Electric dipole moments are extremely sensitive probes for additional sources of CP violation in new physics models. The multi-scale problem of relating the high-precision measurements with neutrons, atoms and molecules to fundamental parameters can be approached model-independently to a large extent; however, care must be taken to include the uncertainties from especially nuclear and QCD calculations properly. The resulting bounds on fundamental parameters are illustrated in the context of Two-Higgs-Doublet models.

hep-ph↗

arXiv2015

Family non-universal Z' models with protected flavor-changing interactions

We define a new class of $Z'$ models with neutral flavor-changing interactions at tree level in the down-quark sector. They are related in an exact way to elements of the quark mixing matrix due to an underlying flavored $U(1)'$ gauge symmetry, rendering these models particularly predictive. The same symmetry implies lepton-flavor non-universal couplings, fully determined by the gauge structure of the model. Our models allow to address presently observed deviations from the SM and specific correlations among the new physics contributions to the Wilson coefficients $C_{9,10}^{(\prime) \ell}$ can be tested in $b \to s \ell^+ \ell^-$ transitions. We furthermore predict lepton-universality violations in $Z'$ decays, testable at the LHC.

hep-ph↗

arXiv2015

B->Kπll in and outside the K* window

We study the impact of B->Kpill decays on B->K*(->Kpi)ll, taking into account the K* at finite width. Interference effects can generically be sizable, up to O(10%), but are reduced in several ratios of observables of the angular distribution. Information on strong phases is central to control interference effects, which cannot be removed by sideband subtractions. We point out ways to probe the strong phases; only a single one is required to describe leading effects in the region of low hadronic recoil. We find that recent LHCb data on the B0->K*0mumu angular observables at low recoil are in good agreement with the standard model.

hep-ph↗

arXiv2015

Signatures of a nonstandard Higgs from flavor physics

We examine the constraints coming from incorporating the full Standard Model gauge symmetry into the effective field theory description of flavor processes, using semileptonic decays as paradigmatic examples. Depending on the dynamics triggering electroweak symmetry breaking, different patterns of correlations between the Wilson coefficients arise. Interestingly, this implies that flavor experiments are capable of shedding light upon the nature of the Higgs boson without actually requiring Higgs final states. Furthermore, the observed correlations can simplify model-independent analyses of these decays.

hep-ph↗

arXiv2015

Standard Model Predictions and New Physics Sensitivity in B->DD Decays

An extensive model-independent analysis of B->DD decays is carried out employing SU(3) flavour symmetry, including symmetry-breaking corrections. Several theoretically clean observables are identified which allow for testing the Standard Model. These include the known time-dependent CP asymmetries, the penguin pollution of which can be controlled in this framework, but notably also quasi-isospin relations which are experimentally well accessible and unaffected by symmetry-breaking corrections. Theoretical assumptions can be kept to a minimum and controlled by additional sum rules. Available data are used in global fits to predict the branching ratio for the B0->DsDs decay as well as several CP asymmetries which have not been measured so far, and future prospects are analyzed.

hep-ph↗

arXiv2014

The $\bar B \to \bar K π\ell \ell$ and $\bar B_s \to \bar K K \ell \ell$ distributions at low hadronic recoil

The rare multi-body decays B->K pi ll and B_s->K K ll are both important as backgrounds to precision analyses in the benchmark modes B->K* ll and B_s->phi ll as well as sensitive probes of flavor physics in and beyond the standard model. We work out non-resonant contributions to B->K pi ll and B_s->K K ll amplitudes, where l=e,mu, at low hadronic recoil in a model-independent way. Using the operator product expansion in 1/m_b, we present expressions for the full angular distribution. The latter allows to probe new combinations of |Delta B|=|Delta S|=1 couplings and gives access to strong phases between non-resonant and resonant contributions. Exact endpoint relations between transversity amplitudes based on Lorentz invariance are obtained. Several phenomenological distributions including those from the angular projections to the S-, P-, D-waves are given. Standard model branching ratios for non-resonant B->K pi ll and B_s->K K ll decays are found to be in the few 10^{-8} region, but drop significantly if cuts around the K* or phi mass are employed. Nevertheless, the non-resonant contributions to B->K pi ll provide the dominant background in the B->K* ll signal region with respect to the low mass scalars. In B_s->K K ll, the narrowness of the phi allows for more efficient background control. We briefly discuss lepton-flavor non-universal effects, also in view of the recent data on R_K.

hep-ph↗

arXiv2014

The Electron EDM and EDMs in Two-Higgs-Doublet Models

Electric dipole moments constitute highly sensitive probes for CP-violating effects beyond the Standard Model. The upper limits obtained in various precision experiments can therefore be used to strongly restrict new physics models. However, relating the experimental information to parameters of a specific model is complicated by the presence of various sources for EDMs as well as large theory uncertainties in some of the relevant matrix elements. In this article, we address both issues for the EDMs of heavy paramagnetic systems, where it is possible to include subleading contributions, thereby model-independently extracting the electron EDM. We furthermore use expressions for the presently phenomenologically relevant EDMs with conservative estimates for the theoretical uncertainties to place constraints on CP-violating phases in the context of Two-Higgs-Doublet models.

hep-ph↗