vs. as a probe of a scalar mediator dark-matter scenario

Alexander Berezhnoy; Dmitri Melikhov

doi:10.1209/0295-5075/ad1d03

All issues

Volume 145 / No 1 (January 2024)

EPL, 145 1 (2024) 14001

Abstract

Issue		EPL Volume 145, Number 1, January 2024


Article Number		14001
Number of page(s)		4
Section		Nuclear and plasma physics, particles and fields
DOI		https://doi.org/10.1209/0295-5075/ad1d03
Published online		07 February 2024

EPL, 145 (2024) 14001

$B\to K^{\boldsymbol {*}} M_{X}$ vs. $B \to K M_{X}$ as a probe of a scalar mediator dark-matter scenario

Alexander Berezhnoy¹ and Dmitri Melikhov¹^,2^,3 (dmitri_melikhov@gmx.de)

¹ D. V. Skobeltsyn Institute of Nuclear Physics, M. V. Lomonosov Moscow State University 119991, Moscow, Russia
² Joint Institute for Nuclear Research - 141980 Dubna, Russia
³ Faculty of Physics, University of Vienna - Boltzmanngasse 5, A-1090 Vienna, Austria

Received: 5 November 2023
Accepted: 10 January 2024

Abstract

Recently, Belle II reported the observation of the decay $B\to K M_{X}$ , where M_X is the missing mass, with the branching ratio much exceeding ${\cal {B}}(B\to K \nu \bar \nu )$ which is the only Standard Model (SM) process contributing to this reaction. If confirmed, this might be an indication of new non-SM particles produced in this decay. One of the possible explanations of the observed effect could be light dark-matter (DM) particles produced via a scalar mediator field. We give simple arguments, that a combined analysis of the $B\to K M_{X}$ and $B\to K^* M_{X}$ reactions would be a clean probe of the scalar mediator scenario: i) making use of an observed value ${\cal {B}}(B\to K M_{X})\simeq5.4\,\, {\cal {B}}(B\to K \nu \bar \nu )_{\textrm {SM}}$ and ii) assuming that the effect is due to the light dark-matter coupling to the top quark via a scalar mediator field, one finds an upper limit ${\cal {B}}(B\to K^* M_{X}) < 2.8\,\, {\cal {B}}(B\to K^* \nu \bar \nu )_{\textrm {SM}}$ . Within the discussed scenario, this upper limit does not depend on the mass of the scalar mediator nor on the specific details of the unobserved dark-matter particles in the final state.

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