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/ψK or B→K⁎γ decays specifically.
A
bstract
Electric dipole moments constitute a competitive method to search for new physics, being particularly sensitive to new
CP
-violating phases. Given the experimental and theoretical progress ...in this field and more generally in particle physics, the necessity for more reliable bounds than the ones usually employed emerges. We therefore propose an improved extraction of the electric dipole moment of the electron and the relevant coefficient of the electron-nucleon coupling, taking into account theoretical uncertainties and possible cancellations, to be used in model-dependent analyses. Specifically, we obtain at 95% C.L. |
d
e
| ≤ 0.14 × 10
−26
e
cm with present data, which is very similar to the bound typically quoted from the YbF molecule, but obtained in a more conservative manner. We examine furthermore in detail the prospects for improvements and derive upper limits for the dipole moments of several paramagnetic systems presently under investigation, i.e. cesium, rubidium and francium.
The Vcb puzzle: An update Gambino, Paolo; Jung, Martin; Schacht, Stefan
Physics letters. B,
08/2019, Letnik:
795
Journal Article
Recenzirano
Odprti dostop
We discuss the impact of the recent untagged analysis of B0→D⁎lν¯l decays by the Belle Collaboration on the extraction of the CKM element |Vcb| and provide updated SM predictions for the b→cτν ...observables R(D⁎), Pτ, and FLD⁎. The value of |Vcb| that we find is about 2σ from the one from inclusive semileptonic B decays, and is very sensitive to the slope of the form factor at zero recoil which should soon become available from lattice calculations.
A
bstract
B
decays proceeding via
b
→
cℓν
transitions with
ℓ
=
e
or
μ
are tree-level processes in the Standard Model. They are used to measure the CKM element
V
cb
, as such forming an important ...ingredient in the determination of e.g. the unitarity triangle; hence the question to which extent they can be affected by new physics contributions is important, specifically given the long-standing tension between
V
cb
determinations from inclusive and exclusive decays and the significant hints for lepton flavour universality violation in
b
→
cτ ν
and
b
→
sℓℓ
decays. We perform a comprehensive model-independent analysis of new physics in
b
→
cℓν
, considering all combinations of scalar, vector and tensor interactions occuring in single-mediator scenarios. We include for the first time differential distributions of
B
→
D
∗
ℓν
angular observables for this purpose. We show that these are valuable in constraining non-standard interactions. Specifically, the zero-recoil endpoint of the
B
→
Dℓν
spectrum is extremely sensitive to scalar currents, while the maximum-recoil endpoint of the
B
→
D
∗
ℓν
spectrum with transversely polarized
D
∗
is extremely sensitive to tensor currents. We also quantify the room for
e
-
μ
universality violation in
b
→
cℓν
transitions, predicted by some models suggested to solve the
b
→
cτ ν
anomalies, from a global fit to
B
→
Dℓν
and
B
→
D
∗
ℓν
for the first time. Specific new physics models, corresponding to all possible tree-level mediators, are also discussed. As a side effect, we present
V
cb
determinations from exclusive
B
decays, both with frequentist and Bayesian statistics, leading to compatible results. The entire numerical analysis is based on open source code, allowing it to be easily adapted once new data or new form factors become available.
Machine learning approaches are increasingly used to extract patterns and insights from the ever-increasing stream of geospatial data, but current approaches may not be optimal when system behaviour ...is dominated by spatial or temporal context. Here, rather than amending classical machine learning, we argue that these contextual cues should be used as part of deep learning (an approach that is able to extract spatio-temporal features automatically) to gain further process understanding of Earth system science problems, improving the predictive ability of seasonal forecasting and modelling of long-range spatial connections across multiple timescales, for example. The next step will be a hybrid modelling approach, coupling physical process models with the versatility of data-driven machine learning.
Global fit to b → cτν transitions Murgui, Clara; Peñuelas, Ana; Jung, Martin ...
The journal of high energy physics,
09/2019, Letnik:
2019, Številka:
9
Journal Article
Recenzirano
Odprti dostop
A
bstract
We perform a general model-independent analysis of
b
→
cτ
ν
¯
τ
transitions, including measurements of ℛ
D
, ℛ
D
∗
, their
q
2
differential distributions, the recently measured longitudinal
...D
* polarization
F
L
D
∗
, and constraints from the
B
c
→
τ
ν
¯
τ
lifetime, each of which has significant impact on the fit. A global fit to a general set of Wilson coefficients of an effective low-energy Hamiltonian is presented, the solutions of which are interpreted in terms of hypothetical new-physics mediators. From the obtained results we predict selected
b
→
cτ
ν
¯
τ
observables, such as the baryonic transition
Λ
b
→
Λ
c
τ
ν
¯
τ
, the ratio ℛ
J
/
ψ
, the forward-backward asymmetries
A
FB
D
∗
, the
τ
polarization asymmetries
P
τ
D
∗
, and the longitudinal
D
* polarization fraction
F
L
D
∗
. The latter shows presently a slight tension with any new-physics model, such that an improved measurement could have an important impact. We also discuss the potential change due the very recently announced preliminary
ℛ
D
∗
measurement by the Belle collaboration.
A
bstract
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 paramagnetic 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.
To elucidate the redundancy in the components for the targeting of membrane proteins to the endoplasmic reticulum (ER) and/or their insertion into the ER membrane under physiological conditions, we ...previously analyzed different human cells by label-free quantitative mass spectrometry. The HeLa and HEK293 cells had been depleted of a certain component by siRNA or CRISPR/Cas9 treatment or were deficient patient fibroblasts and compared to the respective control cells by differential protein abundance analysis. In addition to clients of the SRP and Sec61 complex, we identified membrane protein clients of components of the TRC/GET, SND, and PEX3 pathways for ER targeting, and Sec62, Sec63, TRAM1, and TRAP as putative auxiliary components of the Sec61 complex. Here, a comprehensive evaluation of these previously described differential protein abundance analyses, as well as similar analyses on the Sec61-co-operating EMC and the characteristics of the topogenic sequences of the various membrane protein clients, i.e., the client spectra of the components, are reported. As expected, the analysis characterized membrane protein precursors with cleavable amino-terminal signal peptides or amino-terminal transmembrane helices as predominant clients of SRP, as well as the Sec61 complex, while precursors with more central or even carboxy-terminal ones were found to dominate the client spectra of the SND and TRC/GET pathways for membrane targeting. For membrane protein insertion, the auxiliary Sec61 channel components indeed share the client spectra of the Sec61 complex to a large extent. However, we also detected some unexpected differences, particularly related to EMC, TRAP, and TRAM1. The possible mechanistic implications for membrane protein biogenesis at the human ER are discussed and can be expected to eventually advance our understanding of the mechanisms that are involved in the so-called Sec61-channelopathies, resulting from deficient ER protein import.
We perform a comprehensive analysis of scalar contributions in b→cτν transitions including the latest measurements of R(D(⁎)), the q2 differential distributions in B→D(⁎)τν, the τ polarization ...asymmetry for B→D⁎τν, and the bound derived from the total width of the Bc 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 Bc width present a slight tension with the current data on B→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→D(⁎)τν decays or additional decay modes like the baryonic Λb→Λcτν and the inclusive B→Xcτν decays. We also analyze scalar contributions in b→uτν transitions, including the latest measurements of B→τν, providing predictions for Λb→pτν and B→πτν decays. The potential complementarity between the b→u and b→c sectors is finally investigated once assumptions about the flavour structure of the underlying theory are made.
The Orbiting Carbon Observatory-2 (OCO-2), launched in July 2014, is capable of measuring Solar-Induced chlorophyll Fluorescence (SIF), a functional proxy for terrestrial gross primary productivity ...(GPP). Although its primary mission is to measure the column-averaged mixing ratio of CO2 (Xco2) to constrain global carbon source/sink distribution, one of the OCO-2 spectrometers allows for a robust SIF retrieval solely based on solar Fraunhofer lines. Here we present a technical overview of the OCO-2 SIF product, aiming to provide the scientific community guidance on best practices for data analysis, interpretation, and application. This overview consists of the retrieval algorithms, OCO-2 specific bias correction, retrieval uncertainty evaluation, cross-mission comparison with other existing SIF products, and a global-scale examination of the SIF-GPP relationship. With the initial three years of data (September 2014 onward), we compared OCO-2 SIF with retrievals from Greenhouse Gases Observing Satellite (GOSAT) and Global Ozone Monitoring Experiment-2 (GOME-2), and examined its relationship with FLUXCOM and MODIS GPP datasets. Our results show that OCO-2 SIF, along with GOSAT products, closely resemble the mean spatial and temporal patterns of FLUXCOM GPP from regions to the globe. Compared with GOME-2, however, OCO-2 depicts a more realistic spatial contrast between the tropics and extra-tropics. The linear relationship between OCO-2 SIF and existing modeled GPP products diverges somewhat across biomes at the global scale, consistent with previous GOSAT or GOME-2 based findings when modeled GPP products were used, but in contrast to a consistent cross-biome SIF-GPP relationship obtained at flux tower sites with OCO-2 products. This contrast suggests a critical need to reconcile differences in diverse SIF and GPP products and the relationships among them. Overall, the OCO-2 SIF products are robust and valuable for monitoring the global terrestrial carbon cycle and for constraining the carbon source/sink strengths of the Earth system. Finally, insights are offered for future satellite missions optimized for SIF retrievals.
•We present a technical overview of the OCO-2 SIF product and evaluate its fidelity.•The retrieval precision of OCO-2 is considerably improved over existing products.•The SIF-GPP relationship diverges across biomes if modeled GPP products are used.
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