Higher-Twist Effects in Light-Cone Sum Rule for the B→πB\to\pi Form Factor

We calculate the higher-twist corrections to the QCD light-cone sum rule for the $B \to \pi$ transition form factor. The light-cone expansion of the massive quark propagator in the external gluonic field is extended to include new terms containing the derivatives of gluon-field strength. The resulting analytical expressions for the twist-5 and twist-6 contributions to the correlation function are obtained in a factorized approximation, expressed via the product of the lower-twist pion distribution amplitudes and the quark-condensate density. The numerical analysis reveals that new higher-twist effects for the $B \to \pi$ form factor are strongly suppressed. This result justifies the conventional truncation of the operator product expansion in the light-cone sum rules up to twist-4 terms.Comment: 14 pages, 2 figures, 1 tabl

Bs→KℓνℓB_{s}\to K \ell \nu_\ell and B(s)→π(K)ℓ+ℓ−B_{(s)} \to \pi (K) \ell^+\ell^- decays at large recoil and CKM matrix elements

We provide hadronic input for the $B$-meson semileptonic transitions to a light pseudoscalar meson at large recoil. The $B_s\to K$ form factor calculated from QCD light-cone sum rule is updated, to be used for a $|V_{ub}|$ determination from the $B_s\to K \ell \nu$ width. Furthermore, we calculate the hadronic input for the binned observables of $B \to \pi \ell^+ \ell^-$ and $B \to K \ell^+ \ell^-$. In addition to the form factors, the nonlocal hadronic matrix elements are obtained, combining QCD factorization and light-cone sum rules with hadronic dispersion relations. We emphasize that, due to nonlocal effects, the ratio of branching fractions of these decays is not sufficient for an accurate extraction of the $|V_{td}/V_{ts}|$ ratio. Instead, we suggest to determine the Wolfenstein parameters $A,\rho,\eta$ of the CKM matrix, combining the branching fractions of $B \to K \ell^+ \ell^-$ and $B \to \pi \ell^+ \ell^-$ with the direct $CP$-asymmetry in the latter decay. We also obtain the hadronic matrix elements for a yet unexplored channel $B_s \to K \ell^+ \ell^-$.Comment: 21 pages, 4 figures, 5 tables, a few comments and references addded, version accepted for publication in JHE

Disintegration of beauty: a precision study

We update the Standard Model (SM) predictions for $B$-meson lifetimes within the heavy quark expansion (HQE). Including for the first time the contribution of the Darwin operator, SU(3)$_F$ breaking corrections to the matrix element of dimension-six four-quark operators and the so-called eye-contractions, we obtain for the total widths \Gamma (B^+) = (0.58^{+0.11}_{-0.07}) \, \mbox{ps}^{-1}, \Gamma (B_d) = (0.63^{+0.11}_{-0.07}) \, \mbox{ps}^{-1}, \Gamma (B_s) = (0.63^{+0.11}_{-0.07}) \, \mbox{ps}^{-1}, and for the lifetime ratios $\tau (B^+) / \tau (B_d) = 1.086 \pm 0.022$, $\tau (B_s) / \tau (B_d) = 1.003 \pm 0.006 \, (1.028 \pm 0.011)$. The two values for the last observable arise from using two different sets of input for the non-perturbative parameters $\mu_\pi^2(B_d)$, $\mu_G^2(B_d)$, and $\rho_D^3(B_d)$ as well as from different estimates of the SU(3)$_F$ breaking in these parameters. Our results are overall in very good agreement with the corresponding experimental data, however, there seems to emerge a tension in $\tau (B_s)/\tau (B_d)$ when considering the second set of input parameters. Specifically, this observable is extremely sensitive to the size of the parameter $\rho_D^3 (B_d)$ and of the SU(3)$_F$ breaking effects in $\mu_\pi^2$, $\mu_G^2$ and $\rho_D^3$; hence, it is of utmost importance to be able to better constrain all these parameters. In this respect, an extraction of $\mu_\pi^2 (B_s), \mu_G^2 (B_s), \rho_D^3 (B_s)$ from future experimental data on inclusive semileptonic $B_s$-meson decays or from direct non-perturbative calculations, as well as more insights about the value of $\rho_D^3 (B)$ extracted from fit, would be very helpful in reducing the corresponding theory uncertainties.Comment: 35 pages, 5 figures, 7 table

Contribution of the Darwin operator to non-leptonic decays of heavy quarks

We compute the Darwin operator contribution (1/m3b correction) to the width of the inclusive non-leptonic decay of a B meson (B+, Bd or Bs), stemming from the quark flavour-changing transition b → q1q¯¯2q3, where q1, q2 = u, c and q3 = d, s. The key ideas of the computation are the local expansion of the quark propagator in the external gluon field including terms with a covariant derivative of the gluon field strength tensor and the standard technique of the Heavy Quark Expansion (HQE). We confirm the previously known expressions of the 1/m3b contributions to the semi-leptonic decay b → q1ℓν¯¯¯ℓ, with ℓ = e, μ, τ and of the 1/m2b contributions to the non-leptonic modes. We find that this new term can give a sizeable correction of about −4 % to the non-leptonic decay width of a B meson. For Bd and Bs mesons this turns out to be the dominant correction to the free b-quark decay, while for the B+ meson the Darwin term gives the second most important correction — roughly 1/2 to 1/3 of the phase space enhanced Pauli interference contribution. Due to the tiny experimental uncertainties in lifetime measurements the incorporation of the Darwin term contribution is crucial for precision tests of the Standard Model

Taming New Physics in b→cuˉd(s)b \to c \bar u d (s) with τ(B+)/τ(Bd)\tau (B^+)/\tau(B_d) and aslda_{sl}^d

Inspired by the recently observed tensions between the experimental data and the theoretical predictions, based on QCD factorisation, for several colour-allowed non-leptonic $B$-meson decays, we study the potential size of new physics (NP) effects in the decay channels $b \to c \bar{u} d(s)$. Starting from the most general effective Hamiltonian describing the $b \to c \bar{u} d(s)$ transitions, we compute NP contributions to the theoretical predictions of $B$-meson lifetime and of $B$-mixing observables. The well-known lifetime ratio $\tau (B^+)/\tau (B_d)$ and the experimental bound on the semi-leptonic CP asymmetry $a_{sl}^d$, provide strong, complementary constraints on some of the NP Wilson coefficients.Comment: 29 pages, 3 figure

Testing the Standard Model with CP asymmetries in flavor-specific nonleptonic decays

Motivated by recent indications that the rates of color-allowed nonleptonic channels are not in agreement with their Standard Model expectations based on QCD factorization, we investigate the potential to study CP asymmetries with these decays. In the Standard Model, these flavor-specific decays are sensitive to CP violation in B0 ðsÞ –B¯ 0 ðsÞ mixing, which is predicted with low uncertainties and can be measured precisely with semileptonic decays. Allowing beyond Standard Model (BSM) contributions to the nonleptonic decay amplitudes, we derive explicit expressions for the flavor-specific CP asymmetries in a model-independent way. We find that BSM contributions could lead to significant enhancements to the CP asymmetries. Therefore measurements of these quantities and subsequent comparison with the CP asymmetries measured with semileptonic decays have potential to identify BSM effects without relying on Standard Model predictions that might be affected by hadronic effects. In addition, we discuss the experimental prospects, and note the excellent potential for a precise determination of the CP asymmetry in B¯ s → Dþ s π− decays by the LHCb experiment

Probing New Physics in b → d transitions

Recent experimental data on several observables in semileptonic B-meson decays are found to be in tension with the corresponding Standard Model predictions. Most of these deviations are related to b → c and b → s flavour changing transitions. In this work, we estimate possible New Physics effects in b → dμ+μ− flavour changing neutral currents. We parametrize NP contributions in a model-independent way and determine the allowed ranges of corresponding Wilson coefficients from the data on the exclusive B±→ π±μ+μ− decays measured recently by the LHCb collaboration. Afterwards, we investigate the impact of these results on other b → d processes such as the leptonic B0→ μ+μ− decays and B0−B¯¯¯¯0 mixing. As an example, we consider a simplified Z′ model that is found to be consistent with current b → d data in the certain regions of the NP parameter space. In addition, we estimate the correlations between the partial decay widths of B → πμ+μ− and B → K μ+μ− processes to be used for an independent determination of CKM matrix elements as well as for a combined New Physics analysis of both b → d and b → s transitions

Lacustrine Records of Holocene Climate and Environmental Change from the Lofoten Islands, Norway

Lakes sediments from the Lofoten Islands, Norway, can be used to generate well resolved records of past climate and environmental change. This dissertation presents three lacustrine paleoenvironmental reconstructions that show evidence for Holocene climate changes associated with North Atlantic climate dynamics and relative sea-level variations driven by glacio-isostatic adjustment. This study also uses distal tephra deposits (cryptotephra) from Icelandic volcanic eruptions to improve the chronologies of these reconstructions and explores new approaches to crypto-tephrochronology. Past and present conditions at Vikjordvatnet, Fiskebølvatnet, and Heimerdalsvatnet were studied during four field seasons conducted from 2007-2010. Initially, each lake was characterized by measuring water column chemistry, logging annual temperature fluctuations, and conducting bathymetric and seismic surveys. Sediment cores were then collected and analyzed using multiple techniques, including: sediment density, magnetic susceptibility, loss-on-ignition, total carbon and nitrogen, δ13C and δ15N of organic matter, and elemental compositions acquired by scanning X-ray fluorescence. Chronologies were established using radiocarbon dating and tephrochronology. A 13.8 cal ka BP record from Vikjordvatnet provides evidence for glacial activity during the Younger Dryas cold interval and exhibits trends in Ti, Fe, and organic content during the Holocene that correlate with regional millennial-scale climate trends and provide evidence for more rapid events. A 9.7 cal ka BP record from Fiskebølvatnet shows a strong signal of sediment inwashing likely driven by local geomorphic conditions, although there is evidence that increased inwashing at the onset of the Neoglacial could have been associated with increased precipitation. Heimerdalsvatnet provides a record of relative sea-level change. A 7.8 cal ka BP sedimentary record reflects changes in salinity and water column conditions as the lake was isolated and defines sea-level regression following the Tapes transgression. Cryptotephra horizons were identified in sediments of Heimerdalsvatnet, Vikjordvatnet, and Sverigedalsvatn. They were also found in a Viking-age boathouse excavated along the shore of Inner Borgpollen. These include the GA4-85, BIP-24a, SILK-N2, Askja, 860 Layer B, Hekla 1158, Hekla 1104, Vedde Ash, and Saksunarvatn tephra. This research project also explored the use of scanning XRF to locate cryptotephra in lacustrine sediments and presents experimental results of XRF scans of tephra-spiked synthetic sediment cores

Non-factorisable effects in the decays B ¯ s 0 → D s + π − B‾s0→Ds+π− {\overline{B}}_s^0\to {D}_s^{+}{\pi}^{-} and B ¯ 0 → D + K − B‾0→D+K− {\overline{B}}^0\to {D}^{+}{K}^{-} from LCSR

Abstract In light of the current discrepancies between the recent predictions based on QCD factorisation (QCDF) and the experimental data for several non-leptonic colour-allowed two-body B-meson decays, we obtain new determinations of the non-factorisable soft-gluon contribution to the decays B ¯ s 0 → D s + π − $${\overline{B}}_s^0\to {D}_s^{+}{\pi}^{-}$$ and B ¯ 0 → D + K − $${\overline{B}}^0\to {D}^{+}{K}^{-}$$ , using the framework of light-cone sum rule (LCSR), with a suitable three-point correlation function and B-meson light-cone distribution amplitudes. In particular, we discuss the problem associated with a double light-cone (LC) expansion of the correlator, and motivate future determinations of the three-particle B-meson matrix element with the gluon and the spectator quark aligned along different light-cone directions. Performing a LC-local operator product expansion of the correlation function, we find, for both modes considered, the non-factorisable part of the amplitude to be sizeable and positive, however, with very large systematic uncertainties. Furthermore, we also determine for the first time, using LCSR, the factorisable amplitudes at LO-QCD, and thus the corresponding branching fractions. Our predictions are in agreement with the experimental data and consistent with the results based on QCDF, although again within very large uncertainties. In this respect, we provide a rich outlook for future improvements and investigations