Predictions for B_s → K^* ℓ ℓ in non-universal Z' models

2019/12/31 by Ashutosh Kumar Alok, Amol Dighe, Shireen Gangal +1
Physics and Astronomy · #Asymmetry #B meson #Bar (unit) #Branching fraction #Electron #High-Energy Particle Collisions Research #Lepton #Meson #Nuclear physics #Observable #Particle physics #Particle physics theoretical and experimental studies #Physics #Physics beyond the Standard Model #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #Universality (dynamical systems) #hep-ex #hep-ph

paper · pdf · doi:10.1140/epjc/s10052-020-8232-z

published as Eur. Phys. J. C (2020) 80: 682 · 17 pages, 10 figures, journal version

openalex created_date 2019/12/13 · openalex publication_date 2020/07/01 · arxiv created 2020/07/29 · arxiv updated 2020/07/30 · openalex updated_date 2026/08/05

Abstract

Abstract The lepton flavor universality violating (LFUV) measurements R_K <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>R</mml:mi><mml:mi>K</mml:mi></mml:msub></mml:math> and R_K^* <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>R</mml:mi><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:msub></mml:math> in B meson decays can be accounted for in non-universal Z' <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>Z</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math> models. We constrain the couplings of these Z' <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>Z</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math> models by performing a global fit to correlated b → s ℓ ℓ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>b</mml:mi><mml:mo>→</mml:mo><mml:mi>s</mml:mi><mml:mi>ℓ</mml:mi><mml:mi>ℓ</mml:mi></mml:mrow></mml:math> and b → d ℓ ℓ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>b</mml:mi><mml:mo>→</mml:mo><mml:mi>d</mml:mi><mml:mi>ℓ</mml:mi><mml:mi>ℓ</mml:mi></mml:mrow></mml:math> processes, and calculate their possible implications for B_s → K^*ℓ ℓ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>B</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:mo>→</mml:mo><mml:msup><mml:mrow><mml:mover><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow><mml:mo>∗</mml:mo></mml:msup><mml:mi>ℓ</mml:mi><mml:mi>ℓ</mml:mi></mml:mrow></mml:math> observables. For real new physics (NP) couplings, the 1 σ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>σ</mml:mi></mml:math> favored parameters allow the corresponding LFUV ratio R_K^*^(s) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>R</mml:mi><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mi>s</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:msubsup></mml:math> in B_s → K^*ℓ ℓ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>B</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:mo>→</mml:mo><mml:msup><mml:mrow><mml:mover><mml:mrow><mml:mi>K</mml:mi></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow><mml:mo>∗</mml:mo></mml:msup><mml:mi>ℓ</mml:mi><mml:mi>ℓ</mml:mi></mml:mrow></mml:math> to range between 0.8 and 1.2 at low q² <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> . Complex NP couplings improve the best fit only marginally, however they allow a significant enhancement of the branching ratio, while increasing the range of R_K^*^(s) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>R</mml:mi><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mi>s</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:msubsup><mml:mspace/></mml:mrow></mml:math> at low q² <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> to 0.8–1.8. We find that NP could cause zero-crossing in the forward–backward asymmetry A_FB <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>FB</mml:mi></mml:mrow></mml:msub></mml:math> to shift towards lower q² <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>q</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:math> values, and enhancement in the magnitude of integrated A_FB <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>FB</mml:mi></mml:mrow></mml:msub></mml:math> . The CP asymmetry A_CP <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>CP</mml:mi></mml:mrow></mml:msub></mml:math> may be suppressed and even change sign. The simultaneous measurements of integrated R_K^*^(s) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>R</mml:mi><mml:mrow><mml:msup><mml:mi>K</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mi>s</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:msubsup><mml:mspace/></mml:mrow></mml:math> and A_CP <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>A</mml:mi><mml:mrow><mml:mi>CP</mml:mi></mml:mrow></mml:msub></mml:math> values to 0.1 and 1% respectively, would help in constraining the effective NP Wilson coefficient C₉ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>C</mml:mi><mml:mn>9</mml:mn></mml:msub></mml:math> in b → d μ μ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>b</mml:mi><mml:mo>→</mml:mo><mml:mi>d</mml:mi><mml:mi>μ</mml:mi><mml:mi>μ</mml:mi></mml:mrow></mml:math> interactions.

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