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Register a new userBaryon-Number-Violating Nucleon and Dinucleon Decays in a Model with Large Extra Dimensions
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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.
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We consider baryon-number-violating nucleon and dinucleon decays to leptonic final states in the context of a left-right symmetric (LRS) model with large extra dimensions. Specifically, we study (a) nucleon to trilepton decays with $Delta B=-1$ and $Delta L=-3$, and (b) dinucleon to dilepton decays with $Delta B=-2$ and $Delta L=-2$. In the LRS model, $B-L$ is gauged and is spontaneously broken by a Higgs vacuum expectation value $v_R$, which characterizes the scale at which processes violating $B-L$ occur. We show that together with the lower bound on $v_R$ from experimental limits on $n$-$bar n$ oscillations, constraints from searches for other nucleon decay modes imply sufficient suppression of these nucleon to trilepton and dinucleon to dilepton decay modes in this model to agree with experimental bounds.
We study baryon number violating nucleon decays induced by unparticle interactions with the standard model particles. We find that the lowest dimension operators which cause nucleon decays can arise at dimension 6 + (d_s-3/2) with the unparticles being a spinor of dimension d_s=d_U +1/2. For scalar and vector unparticles of dimension d_U, the lowest order operatoers arise at 6+d_U and 7+d_U dimensions,respectively. Comparing the spinor unparticle induced n to O^s_U and experimental bound on invisible decay of a neutron from KamLAND, we find that the scale for unparticle physics is required to be larger than 10^{10} GeV for d_U < 2 if the couplings are set to be of order one. For scalar and vector unparticles, the dominant baryon number violating decay modes are nto bar u + O_U (O^mu_U) and p to e^+ + O_U (O^mu_U). The same experimental bound puts the scales for scalar and vector unparticle to be larger than 10^{7} and 10^{5} GeV for d_U <2 with couplings set to be of order one. Data on, p to e^+ invisible, puts similar constraints on unparticle interactions.
We consider effects of $n-bar n$ oscillations and resultant matter instability due to dinucleons decays. We point out that existing upper bounds on the rates for the dinucleon decays $nn to 2pi^0$, $nn to pi^+pi^-$, and $np to pi^+pi^0$ imply upper bounds on the rates for dinucleon decays to dileptons $nn to e^+ e^-$, $nn to mu^+mu^-$, $nn to u_ell bar u_ell$, and $np to ell^+ u_ell$, where $ell=e, mu, tau$. We present estimates for these upper bounds. Our bounds are substantially stronger than corresponding limits from direct searches.
We study baryon-number-violating processes, including proton and bound neutron decays and $n-bar n$ oscillations, in a left-right-symmetric (LRS) model in which quarks and leptons have localized wavefunctions in extra dimensions. In this model we show that, while one can easily suppress baryon-number-violating nucleon decays well below experimental bounds, this does not suppress $n-bar n$ transitions, which may occur at levels comparable to current limits. This is qualitatively similar to what was found in an extra-dimensional model with a Standard-Model low-energy effective field theory (SMEFT). We show that experimental data imply a lower limit on the mass scale $M_{n bar n}$ characterizing the physics responsible for $n-bar n$ oscillations in the LRS model that is significantly higher than in the extra-dimensional model using a SMEFT and explain the reason for this. Our results provide further motivation for new experiments to search for $n - bar n$ oscillations.
Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R-parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets.
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