Baryon-number-violating nucleon and dinucleon decays in a model with large extra dimensions

Sudhakantha Girmohanta,Robert Shrock

doi:10.1103/physrevd.101.015017

Sudhakantha Girmohanta, Robert Shrock

Open Access

https://doi.org/10.1103/physrevd.101.015017

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Abstract

It is known that limits on baryon-violating nucleon decays do not, in general, imply corresponding suppression of $n - \bar n$ transitions. In the context of a model with fermions propagating in higher dimensions, we investigate a related question, namely the implications of limits on $\Delta L=-1$ proton and bound neutron decays mediated by four-fermion operators for rates of nucleon decays mediated by $k$-fermion operators with $k =6$ and $k=8$. These include a variety of nucleon and dinucleon decays to dilepton and trilepton final states with $\Delta L=-3, \ -2, \ 1$, and $2$. We carry out a low-energy effective field theory analysis of relevant operators for these decays and show that, in this extra-dimensional model, the rates for these decays are strongly suppressed and hence are in accord with experimental limits.

Highlights

The Standard Model (SM), as extended to include nonzero neutrino masses and lepton mixing, agrees with current data, there are many aspects of particle physics that it does not explain
In this paper we have studied several baryon-numberviolating nucleon and dinucleon decays in a model with large extra dimensions, including (i) the ΔL 1⁄4 −3 nucleon decays p → lþ νν0 and n → νν0 ν00 ; (ii) the ΔL 1⁄4 1 nucleon decays p → lþ νν0 and n → νν0 ν00 ; (iii) the ΔL 1⁄4 −2 dinucleon decays pp → ðeþ eþ ; μþ μþ ; eþ μþ ; eþ τþ ; or μþ τþ ), np → lþ ν, and nn → νν0, where lþ 1⁄4 eþ ; μþ, or τþ ; and (iv) the ΔL 1⁄4 2 dineutron decays nn → νν0
Motivated by the earlier finding in Ref. [25] that, even with fermion wave function positions chosen so as to render the rates for baryon-number-violating nucleon decays much smaller than experimental limits, n − noscillations could occur at rates comparable to experimental bounds, we have addressed the generalized question of whether nucleon and dinucleon decays to leptonic final states mediated by six-fermion and eight-fermion operators are sufficiently suppressed to agree with experimental bounds

Summary

INTRODUCTION

The Standard Model (SM), as extended to include nonzero neutrino masses and lepton mixing, agrees with current data, there are many aspects of particle physics that it does not explain. SUDHAKANTHA GIRMOHANTA and ROBERT SHROCK experimental limits In this case, it is the (jΔBj 1⁄4 2) n − noscillations and the corresponding (ΔB 1⁄4 −2) nn and np dinucleon decays that are the main observable effects of baryon number violation, rather than (ΔB 1⁄4 −1) decays of individual nucleons. Using the same extra-dimensional model as in [25], we study a variety of nucleon and dinucleon decays that violate both B and total lepton number L and are mediated by k-fermion operators with k 1⁄4 6 and k 1⁄4 8, respectively. These include the ΔL 1⁄4 −3 nucleon decays p → lþ νν0. In the Appendixes A, B, and D we give relevant integral formulas, color SUð3Þc and weak SUð2ÞL tensors, and present further information on relevant operators

THEORETICAL FRAMEWORK

CONSTRAINTS FROM LIMITS

CONCLUSIONS