We perform an analysis of the consequences of various new physics operators on the lepton flavor violating (LFV) decay modes mediated through <math><mi>b</mi><mo>→</mo><mi>s</mi><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math> transitions. We scrutinize the imprints of the (pseudo)scalar and axial (vector) operators on the exclusive LFV decay channels <math><msub><mrow><mi>B</mi></mrow><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></msub><mo>→</mo><mo>(</mo><mi>ϕ</mi><mo>,</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>,</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>⁎</mo></mrow></msubsup><mo>)</mo><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math> and <math><msub><mrow><mi>Λ</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>→</mo><mi>Λ</mi><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>1</mn></mrow></msub><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math>, where <math><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>,</mo><msub><mrow><mi>ℓ</mi></mrow><mrow><mn>2</mn></mrow></msub></math> represent μ or τ. The new physics parameters are constrained by using the upper limits of the branching fractions of the <math><msub><mrow><mi>B</mi></mrow><mrow><mi>s</mi></mrow></msub><mo>→</mo><mi>τ</mi><mi>μ</mi></math> and <math><mi>B</mi><mo>→</mo><mi>K</mi><mi>τ</mi><mi>μ</mi></math> processes, assuming the new physics couplings to be real. We then explore the key observables such as the branching fractions, the forward-backward asymmetries, and the longitudinal polarization fractions of the <math><mi>B</mi><mo>→</mo><mo>(</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>,</mo><mi>ϕ</mi><mo>,</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mn>2</mn></mrow><mrow><mo>⁎</mo></mrow></msubsup><mo>)</mo><msup><mrow><mi>τ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>∓</mo></mrow></msup></math> decays. In addition, we also investigate the impact of the new physics couplings on the baryonic <math><msub><mrow><mi>Λ</mi></mrow><mrow><mi>b</mi></mrow></msub><mo>→</mo><mi>Λ</mi><msup><mrow><mi>τ</mi></mrow><mrow><mo>±</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>∓</mo></mrow></msup></math> decay channels mediated by the <math><mi>b</mi><mo>→</mo><mi>s</mi></math> quark level transition. With the experimental prospects at LHCb upgrade and Belle II, we also predict the upper limits of the above-discussed observables, which could intrigue the new physics search in these channels.

India

Dhiren Panda

Manas Kumar Mohapatra

Rukmani Mohanta

Exploring the lepton flavor violating decay modes → in SMEFT approach

At present, there are several measurements of B decays that exhibit discrepancies with the predictions of the Standard Model, and suggest the presence of new physics in <math><mi>b</mi><mo>→</mo><mi>s</mi></math> and <math><mi>b</mi><mo>→</mo><mi>c</mi><mo>(</mo><mi>u</mi><mo>)</mo></math> quark level transitions. Motivated by the prospects of the ongoing high-luminosity B factories, we study the exclusive <math><mi>B</mi><mo>→</mo><msub><mrow><mi>a</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mn>1260</mn><mo>)</mo><msup><mrow><mi>ℓ</mi></mrow><mrow><mo>−</mo></mrow></msup><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>ℓ</mi></mrow></msub></math> process within the Standard Model Effective Field Theory (SMEFT) formalism, to understand the sensitivity of various new physics operators. The new physics parameters are constrained by using the experimental branching fractions of the (semi)leptonic <math><mi>B</mi><mo>→</mo><mi>ℓ</mi><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> and <math><mi>B</mi><mo>→</mo><mo>(</mo><mi>π</mi><mo>,</mo><mi>ρ</mi><mo>,</mo><mi>ω</mi><mo>)</mo><mi>ℓ</mi><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> processes (where <math><mi>ℓ</mi><mo>=</mo><mi>e</mi><mo>,</mo><mi>μ</mi><mo>,</mo><mi>τ</mi></math>) which undergo <math><mi>b</mi><mo>→</mo><mi>u</mi><mi>ℓ</mi><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> quark level transitions. We then perform a comprehensive angular analysis of the exclusive <math><mi>B</mi><mo>→</mo><msub><mrow><mi>a</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mn>1260</mn><mo>)</mo><msup><mrow><mi>ℓ</mi></mrow><mrow><mo>−</mo></mrow></msup><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>ℓ</mi></mrow></msub></math> process in the Standard Model and in the presence of various new physics operators. We also provide the predictions and comment on various observables, such as branching ratio, forward-backward asymmetry, and the test of lepton flavor non universality of the <math><mi>B</mi><mo>→</mo><msub><mrow><mi>a</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mn>1260</mn><mo>)</mo><msup><mrow><mi>ℓ</mi></mrow><mrow><mo>−</mo></mrow></msup><msub><mrow><mover><mrow><mi>ν</mi></mrow><mrow><mo>¯</mo></mrow></mover></mrow><mrow><mi>ℓ</mi></mrow></msub></math> channel.

Imprints of new physics operators in the semileptonic process in SMEFT approach

Deep machine learning methods have been studied for the software trigger of the future PANDA experiment at FAIR, using Monte Carlo simulated data from the GEANT-based detector simulation framework PandaRoot. Ten physics channels that cover the main physics topics, including electromagnetic, exotic, charmonium, open charm, and baryonic reaction channels, have been investigated at four different anti-proton beam momenta. Different classification concepts and network architectures have been studied. Finally a residual convolutional neural network with four residual blocks in a binary classification scheme has been chosen due to its extendability, performance and stability. The presented study represents a feasibility study of a completely software-based trigger system. Compared to a conventional selection method, the deep machine learning approach achieved a significant efficiency gain of up to 200%, while keeping the background reduction factor at the required level of 1/1000. Furthermore, it is shown that the use of additional input variables can improve the data quality for subsequent analysis. This study shows that the PANDA software trigger can benefit greatly from the deep machine learning methods.

Germany

China

Peiyong Jiang

Klaus Götzen

Ralf Kliemt

Frank Nerling

Klaus Peters

Deep machine learning for the PANDA software trigger

We evaluate the cross section for the <math><mi>p</mi><mi>p</mi><mo>→</mo><mi>p</mi><mi>p</mi><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo></math> and <math><mi>p</mi><mover><mi>p</mi><mo>¯</mo></mover><mo>→</mo><mi>p</mi><mover><mi>p</mi><mo>¯</mo></mover><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo></math> reactions at near threshold energies relevant for the HADES and PANDA experiments at GSI-FAIR. We assume that at energies close to the threshold the <math><mi>ω</mi><mi>ω</mi><mo>→</mo><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo></math> and <math><msup><mi>ρ</mi><mn>0</mn></msup><msup><mi>ρ</mi><mn>0</mn></msup><mo>→</mo><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo></math> fusion processes are the dominant production mechanisms. The vertex for the <math><mi>V</mi><mi>V</mi><mo>→</mo><msub><mi>f</mi><mn>1</mn></msub></math> coupling is derived from an effective coupling Lagrangian. The <math><msub><mi>g</mi><mrow><mi>ρ</mi><mi>ρ</mi><msub><mi>f</mi><mn>1</mn></msub></mrow></msub></math> coupling constant is extracted from the decay rate of <math><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo><mo>→</mo><msup><mi>ρ</mi><mn>0</mn></msup><mi>γ</mi></math> using the vector-meson-dominance ansatz. We assume <math><msub><mi>g</mi><mrow><mi>ω</mi><mi>ω</mi><msub><mi>f</mi><mn>1</mn></msub></mrow></msub><mo>=</mo><msub><mi>g</mi><mrow><mi>ρ</mi><mi>ρ</mi><msub><mi>f</mi><mn>1</mn></msub></mrow></msub></math>, equality of these two coupling constants, based on arguments from the naive quark model and vector-meson dominance. The amplitude for the <math><mi>V</mi><mi>V</mi><mo>→</mo><msub><mi>f</mi><mn>1</mn></msub></math> fusion, supplemented by phenomenological vertex form factors for the process, is given. The differential cross sections at energies close to the threshold are calculated. In order to determine the parameters of the model the <math><mi>γ</mi><mi>p</mi><mo>→</mo><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo><mi>p</mi></math> reaction is discussed in addition and results are compared with the CLAS data. The possibility of a measurement by HADES@GSI is presented and discussed. We perform a Monte Carlo feasibility simulation of the <math><mi>p</mi><mi>p</mi><mo>→</mo><mi>p</mi><mi>p</mi><msub><mi>f</mi><mn>1</mn></msub></math> reaction for <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>3.46</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with the <math><msub><mi>f</mi><mn>1</mn></msub></math> decaying into the <math><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> (not shown explicitly) and <math><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>η</mi><mo>(</mo><mo>→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup><mo>)</mo></mrow></math> final states using the PLUTO event generator. The latter <math><msub><mi>f</mi><mn>1</mn></msub></math> decay is especially promising as a peak in the <math><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><mi>η</mi></math> mass distribution should be observable by HADES.

Poland

Piotr Lebiedowicz

Otto Nachtmann

Piotr Salabura

Antoni Szczurek

Exclusive <math><msub><mi>f</mi><mn>1</mn></msub><mo>(</mo><mn>1285</mn><mo>)</mo></math> meson production for energy ranges available at the GSI-FAIR with HADES and PANDA