Searching for dark photons in hyperon decays

Abstract

That massless dark photons could exist and have flavor-changing magnetic-dipole couplings to downtype light quarks is an attractive possibility which may be realized in various new-physics scenarios. It is potentially testable not only in kaon processes but also via two-body hyperon decays involving missing energy carried away by the massless dark photon. We explore the latter within a simplified model approach and take into account constraints from the kaon sector. We find that the branching fractions of some of these hyperon modes are allowed to be as high as a few times 10 −4 . Such numbers are likely to be within the sensitivity reaches of ongoing experiments like BESIII and future ones at super charm-tau factories.

Exploring leptoquark effects in hyperon and kaon decays with missing energy

“…(38) are consistent with the indirect upper bounds on the branching fractions of yet-unobserved decay modes of Λ, Σ þ , Ξ 0 , Ξ − , and Ω − , namely 1.4 × 10 −2 , 8.0 × 10 −3 , 3.4 × 10 −4 , 8.3 × 10 −4 , and 1.6 × 10 −2 , respectively, which were inferred in Ref. [54] from the data (at 2 sigmas) on the observed channels [5].…”

Kaon decays shedding light on massless dark photons

“…Subsequently, it was shown in Ref. [15] that these interactions also gave rise to the FCNC decays of hyperons into a lighter baryon plus γ emitted invisibly and that the less restrained of the models could saturate the limits on the couplings inferred from the existing data on hyperon Table 1 The second column exhibits the sums of branching fractions of all the observed decays [43] of the , + , 0 , − , and − hyperons and of the K L and K S mesons. The last column contains the upper limits on the branching fractions of yet-unobserved decays of these hadrons deduced from the numbers in the second column, as explained in the text decays [43].…”

“…In Ref. [15] we have studied such two-body processes and demonstrated that their rates are allowed by present constraints to reach values that are within the sensitivity reach of the ongoing BESIII experiment [32,33]. Analogous transitions can take place in the kaon sector.…”

“…To discuss the impact of the hyperon data more quantitatively, we reproduce here the branching fractions of the aforementioned FCNC hyperon modes calculated in Ref. [15] and expressed in terms of C and C 5 : These transitions, if occur, would be among the yet-unobserved decays of the hyperons. The branching fractions of the latter have approximate maxima which we can determine indirectly from the data on the observed channels quoted by the Particle Data Group [43].…”

“…The massless dark photon, here denoted by γ , is very dissimilar from the massive one because they differ substantially in both theoretical underpinnings and experimental signatures [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. If U(1) D remains unbroken, one can always arrange a linear combination of the dark and SM U(1) gauge bosons such that it has no renormalizable connection to the SM and can then be identified as the massless dark photon [7,9].…”