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Register a new userRenormalization group evolution of dimension-six baryon number violating operators
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We calculate the one-loop anomalous dimension matrix for the dimension-six baryon number violating operators of the Standard Model effective field theory, including right-handed neutrino fields. We discuss the flavor structure of the renormalization group evolution in the contexts of minimal flavor violation and unification.
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We calculate one-loop renormalization factors of three-quark operators, which appear in the low energy effective Lagrangian of the nucleon decay, for $O(a)$-improved quark action and gauge action including six-link loops. This calculation is required to predict the hadronic nucleon decay matrix elements in the continuum regularization scheme using lattice QCD. We present detailed numerical results of the one-loop coefficients for general values of the clover coefficients employing the several improved gauge actions in the Symanzik approach and in the Wilsons renormalization group approach. The magnitudes of the one-loop coefficients for the improved gauge actions show sizable reduction compared to those for the plaquette action.
We obtain the partial-wave unitarity constraints on dimension-six operators stemming from the analyses of vector boson and Higgs scattering processes as well as the inelastic scattering of standard model fermions into electroweak gauge bosons. We take into account all coupled channels, all possible helicity amplitudes, and explore a six-dimensional parameter space of anomalous couplings. Our analysis shows that for those operators affecting the Higgs couplings, present 90% confidence level constraints from global data analysis of Higgs and electroweak data are such that unitarity is not violated if $sqrt{s}leq 3.2;{rm TeV}$. For the purely gauge-boson operator $O_{WWW}$, the present bounds from triple-gauge boson analysis indicate that within its presently allowed 90% confidence level range unitarity can be violated in $fbar f to V V$ at center-of-mass energy $sqrt{s}geq 2.4;{rm TeV}$.
Earlier estimates have argued that the baryon number violating scattering cross-section in the laboratory is exponentially small so it will never be observed, even for incoming 2-particle energy well above the sphaleron energy of 9 TeV. However, we argue in arXiv:1505.03690 that, due to the periodic nature of the sphaleron potential, the event rate for energies above the sphaleron energy may be high enough to be observed in the near future. That is, there is a discrepancy of about 70 orders of magnitude between the two estimates. Here we argue why and how the multi-sphaleron processes are crucial to the event rate estimate, a very important resonant tunneling property that has not been taken into account before. We also summarize the input assumptions and reasoning adopted in our estimate, when compared to the earlier estimates.
We analyze the scattering of fermions, Higgs and electroweak gauge bosons in order to obtain the partial-wave unitarity bounds on dimension-six effective operators, including those involving fermions. We also quantify whether, at the LHC energies, the dimension-six operators lead to unitarity violation after taking into account the presently available constraints on their Wilson coefficients. Our results show that for most dimension-six operators relevant for the LHC physics there is no unitarity violation at the LHC energies, and consequently, there is no need for the introduction of form factors in the experimental and phenomenological analyses, making them model independent. We also identify two operators for which unitarity violation is still an issue at the LHC Run-II.
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.
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