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Contribution of the Darwin operator to non-leptonic decays of heavy quarks (2020)
Journal Article
Lenz, A., Piscopo, M. L., & Rusov, A. V. (2020). Contribution of the Darwin operator to non-leptonic decays of heavy quarks. Journal of High Energy Physics, 2020(12), Article 199. https://doi.org/10.1007/jhep12%282020%29199

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... Read More about Contribution of the Darwin operator to non-leptonic decays of heavy quarks.

Charming new B-physics (2020)
Journal Article
Jäger, S., Kirk, M., Lenz, A., & Leslie, K. (2020). Charming new B-physics. Journal of High Energy Physics, 2020(3), Article 122. https://doi.org/10.1007/jhep03%282020%29122

We give a comprehensive account of the flavour physics of Beyond-Standard-Model (BSM) effects in b → cc¯¯cs transitions, considering the full set of 20 four-quark operators. We discuss the leading-order structure of their RG mixing with each other as... Read More about Charming new B-physics.

∆Ms theory precision confronts flavour anomalies (2019)
Journal Article
Di Luzio, L., Kirk, M., Lenz, A., & Rauh, T. (2019). ∆Ms theory precision confronts flavour anomalies. Journal of High Energy Physics, 2019(12), Article 9. https://doi.org/10.1007/jhep12%282019%29009

Based on recent HQET sum rule and lattice calculations we present updated Standard Model predictions for the mass differences of neutral B mesons: ΔMSMs=(18.4+0.7−1.2)ps−1 and ΔMSMd=(0.533+0.022−0.036)ps−1 study their impact onnew physics models that... Read More about ∆Ms theory precision confronts flavour anomalies.

Delta ACP within the Standard Model and beyond (2019)
Journal Article
Chala, M., Lenz, A., Rusov, A. V., & Scholtz, J. (2019). Delta ACP within the Standard Model and beyond. Journal of High Energy Physics, 2019(7), Article 161. https://doi.org/10.1007/jhep07%282019%29161

In light of the recent LHCb observation of CP violation in the charm sector, we review standard model (SM) predictions in the charm sector and in particular for ∆ACP. We get as an upper bound in the SM |∆ASM CP| ≤ 3.6 × 10−4 , which can be compared t... Read More about Delta ACP within the Standard Model and beyond.

Bs mixing observables and |Vtd/Vts| from sum rules (2019)
Journal Article
King, D., Lenz, A., & Rauh, T. (2019). Bs mixing observables and |Vtd/Vts| from sum rules. Journal of High Energy Physics, 2019(5), Article 34. https://doi.org/10.1007/jhep05%282019%29034

We consider the effects of a non-vanishing strange-quark mass in the determination of the full basis of dimension six matrix elements for Bs mixing, in particular we get for the ratio of the V − A Bag parameter in the Bs and Bd system: B s Q1 /B d Q1... Read More about Bs mixing observables and |Vtd/Vts| from sum rules.

Updated Bs -mixing constraints on new physics models for b→sℓ+ℓ− anomalies (2018)
Journal Article
Di Luzio, L., Kirk, M., & Lenz, A. (2018). Updated Bs -mixing constraints on new physics models for b→sℓ+ℓ− anomalies. Physical Review D, 97(9), Article 095035. https://doi.org/10.1103/physrevd.97.095035

Many new physics models that explain the intriguing anomalies in the b-quark flavor sector are severely constrained by Bs mixing, for which the Standard Model prediction and experiment agreed well until recently. The most recent Flavour Lattice Avera... Read More about Updated Bs -mixing constraints on new physics models for b→sℓ+ℓ− anomalies.

Charming new physics in rare B decays and mixing? (2018)
Journal Article
Jäger, S., Leslie, K., Kirk, M., & Lenz, A. (2018). Charming new physics in rare B decays and mixing?. Physical Review D, 97(1), Article 015021. https://doi.org/10.1103/physrevd.97.015021

We conduct a systematic study of the impact of new physics in quark-level b → ccs¯ transitions on B physics, in particular rare B decays and B-meson lifetime observables. We find viable scenarios where a sizable effect in rare semileptonic B decays c... Read More about Charming new physics in rare B decays and mixing?.

Double-charming Higgs boson identification using machine-learning assisted jet shapes (2018)
Journal Article
Lenz, A., Spannowsky, M., & Tetlalmatzi-Xolocotzi, G. (2018). Double-charming Higgs boson identification using machine-learning assisted jet shapes. Physical Review D, 97(1), Article 016001. https://doi.org/10.1103/physrevd.97.016001

We study the possibility of identifying a boosted resonance that decays into a charm pair against different sources of background using QCD event shapes, which are promoted to jet shapes. Using a set of jet shapes as input to a boosted decision tree,... Read More about Double-charming Higgs boson identification using machine-learning assisted jet shapes.

Dimension-six matrix elements for meson mixing and lifetimes from sum rules (2017)
Journal Article
Kirk, M., Lenz, A., & Rauh, T. (2017). Dimension-six matrix elements for meson mixing and lifetimes from sum rules. Journal of High Energy Physics, 2017(12), Article 68. https://doi.org/10.1007/jhep12%282017%29068

The hadronic matrix elements of dimension-six ∆F = 0, 2 operators are crucial inputs for the theory predictions of mixing observables and lifetime ratios in the B and D system. We determine them using HQET sum rules for three-point correlators. The r... Read More about Dimension-six matrix elements for meson mixing and lifetimes from sum rules.

On the ultimate precision of meson mixing observables (2016)
Journal Article
Jubb, T., Kirk, M., & Lenz, A. (2017). On the ultimate precision of meson mixing observables. Nuclear Physics B, 915, 431-453. https://doi.org/10.1016/j.nuclphysb.2016.12.020

Meson mixing is considered to be an ideal testing ground for new physics searches. Experimental precision has greatly increased over the recent years, exceeding in several cases the theoretical precision. A possible limit in the theoretical accuracy... Read More about On the ultimate precision of meson mixing observables.

CP violation in the B0s system (2016)
Journal Article
Artuso, M., Borissov, G., & Lenz, A. (2016). CP violation in the B0s system. Reviews of Modern Physics, 88(4), Article 045002. https://doi.org/10.1103/revmodphys.88.045002

Experimental and theoretical studies of CP violation in the B0s system are reviewed. Updated predictions for the mixing parameters of the B0s mesons expected in the standard model (SM) are given, namely, the mass difference ΔMSMs=18.3±2.7  ps−1, the... Read More about CP violation in the B0s system.

Theory Overview (2016)
Presentation / Conference Contribution
Lenz, A., & Carbone, A. (2016, September). Theory Overview. Presented at VIII International Workshop On Charm Physics (CHARM 2016), Bologna, Italy

We set the scene for theoretical issues in charm physics that were discussed at CHARM 2016 in Bologna. In particular we emphasize the importance of improving our understanding of standard model contributions to numerous charm observables and we discu... Read More about Theory Overview.

New physics effects in tree-level decays and the precision in the determination of the quark mixing angle γ (2015)
Journal Article
Brod, J., Lenz, A., Tetlalmatzi-Xolocotzi, G., & Wiebusch, M. (2015). New physics effects in tree-level decays and the precision in the determination of the quark mixing angle γ. Physical Review D, 92(3), Article 033002. https://doi.org/10.1103/physrevd.92.033002

We critically review the assumption that no new physics is acting in tree-level B-meson decays and study the consequences for the ultimate precision in the direct determination of the Cabibbo-Kobayashi-Maskawa (CKM) angle γ. In our exploratory study... Read More about New physics effects in tree-level decays and the precision in the determination of the quark mixing angle γ.

Lifetimes and Heavy Quark Expansion (2015)
Book Chapter
Lenz, A. (2015). Lifetimes and Heavy Quark Expansion. In I. Bigi, P. Gambino, & T. Mannel (Eds.), QCD and heavy quarks : in memoriam Nikolai Uraltsev (63-109). World Scientific Publishing

Kolya Uraltsev was one of the inventors of the Heavy Quark Expansion (HQE), that describes inclusive weak decays of hadrons containing heavy quarks and in particular lifetimes. Besides giving a pedagogic introduction into the subject, we review the d... Read More about Lifetimes and Heavy Quark Expansion.

Lifetimes and heavy quark expansion (2015)
Journal Article
Lenz, A. (2015). Lifetimes and heavy quark expansion. International Journal of Modern Physics A, 30(10), https://doi.org/10.1142/s0217751x15430058

Kolya Uraltsev was one of the inventors of the Heavy Quark Expansion (HQE), that describes inclusive weak decays of hadrons containing heavy quarks and in particular lifetimes. Besides giving a pedagogic introduction to the subject, we review the dev... Read More about Lifetimes and heavy quark expansion.

Investigating bounds on decoherence in quantum mechanics via B and D-mixing (2014)
Journal Article
Lenz, A., Hodges, D., Hulme, D., Kvedaraite, S., Richings, J., Shen Woo, J., & Waite, P. (2014). Investigating bounds on decoherence in quantum mechanics via B and D-mixing. Nuclear Physics B, 888, 129-136. https://doi.org/10.1016/j.nuclphysb.2014.09.007

We investigate bounds on decoherence in quantum mechanics by studying B and D-mixing observables, making use of many precise new measurements, particularly from the LHC and B factories. In that respect we show that the stringent bounds obtained by a... Read More about Investigating bounds on decoherence in quantum mechanics via B and D-mixing.

Selected Topics in Heavy Flavour Physics (2014)
Journal Article
Lenz, A. (2014). Selected Topics in Heavy Flavour Physics. Journal of Physics G: Nuclear and Particle Physics, 41(10), https://doi.org/10.1088/0954-3899/41/10/103001

We review the status of flavour physics in spring 2014. The numerous accurate new measurements of flavour experiments have enabled us to test our theoretical understanding of flavour processes with an unprecedented precision. At first sight the domin... Read More about Selected Topics in Heavy Flavour Physics.