A statistical analysis of the minimal SUSY B–L theory

Abstract

The structure of the B-L minimal supersymmetric Standard Model (MSSM) theoryspecifically, the relevant mass scales and soft supersymmetric breaking parameters -is discussed. The space of initial soft parameters is explored at the high scale using random statistical sampling subject to a constraint on the range of dimensionful parameters. For every chosen initial point, the complete set of renormalization group equations is solved. The low energy results are then constrained to be consistent with present experimental data. It is shown that a large set of initial conditions satisfy these constraints and lead to acceptable low energy particle physics. Each such initial point has explicit predictions, such as the exact physical sparticle spectrum which is presented for two such points. There are also statistical predictions for the masses of the sparticles and the LSP species which are displayed as histograms. Finally, the fine-tuning of the μ parameter -which is always equivalent to or smaller than in the MSSM -is discussed.An ad hoc Z 2 symmetry -R-parity is invoked in the minimal supersymmetric Standard Model (MSSM) to eliminate certain dimension four operators, which, if present, would induce unobserved rapid proton decay. This leads to the important question: is there a natural explanation for R-parity? Note that R-parity is contained as a finite subgroup of the Abelian group U(1) B-L , and that U(1) B−L can be imposed as a global symmetry of both the MSSM and the right-handed neutrino extended MSSM. One expects, however, that a continuous symmetry of the Lagrangian will appear in its local form; that is, as a gauge symmetry. It has long been known that the MSSM is anomalous under this local symmetry, whereas ‡ Corresponding author 1550085-1 B. A. Ovrut, A. Purves & S. Spinnerthe MSSM extended by three right-handed neutrino chiral multiplets with gauged U(1) B-L -henceforth referred to as the B-L MSSM is anomaly free and renormalizable. Furthermore, it is the minimal such theory. If the gauged U(1) B-L symmetry can be spontaneously broken, then the B-L MSSM gives a natural explanation for the suppression of dimension four proton decay, that is, it is forbidden by gauge invariance rather than by an ad hoc finite symmetry. This makes the B-L MSSM very attractive from both a theoretical and phenomenological perspective.The B-L MSSM was introduced from a "bottom-up" phenomenological point of view in Refs. 1 and 2. It was also found from a "top-down" viewpoint to be the low-energy theory associated with a class of smooth vacua of the E 8 × E 8 heterotic superstring. 3-5 In addition, it was shown 6-8 that the "soft" supersymmetry breaking operators associated with this low-energy theory can radiatively induce -via a nonvanishing vacuum expectation value for a right-handed sneutrino -the breakdown of the U(1) B-L symmetry. Since the sneutrino has odd B-L charge, R-parity is spontaneously broken at a scale that is naturally consistent with both electroweak breaking and the bounds on proton decay. In Ref. 9, an analysis ...

The R-parity violating decays of charginos and neutralinos in the B-L MSSM

“…As discussed in [38,43,44,52,66], it follows from the above Lagrangian that the third family right-handed neutrino and the three left-chiral neutrinos ν i , i = 1, 2, 3 mix with the fermionic superpartners of the neutral gauge bosons and with the up-and down-neutral Higgsinos. In other words, the neutralinos now mix with the neutral fermions of the standard model.…”

“…We conclude that the B − L MSSM is the simplest possible phenomenologically realistic low energy theory of heterotic superstring/M-theory; being the exact MSSM with right-handed neutrinos and spontaneously broken R-parity This theory was originally presented in the series of papers [13,[39][40][41][42][43][44]. It is interesting to point out that the B − L MSSM was also constructed from a "bottom-up" point of view, completely unrelated to superstring theory [45][46][47][48][49][50].…”

“…The electroweak gauge boson masses were obtained, as discussed above, by fine-tuning the parameter µ. For example, a typical value of the fine-tuning of µ is of the order of 1 in 1000 [43]. However, one might also be concerned that getting the Higgs mass correct might require some other fine-tuning of the 24 initial parameters that may not be apparent.…”

The minimal SUSY B − L model: from the unification scale to the LHC

“…The results will be examined to determine the subset of the parameter space that, sequentially, 1) breaks B − L symmetry at a scale consistent with experiment, 2) breaks electroweak symmetry, 3) has all sparticle masses above their present experimental lower bounds and 4) predicts the mass of the lightest neutral Higgs scalar to be within 2σ standard deviation from the ATLAS measured value of 125.36 GeV. A small subset of important results from this statistical scan were given in [33]. Here, we give present the details of the method use, as well as a wide array of new results and experimental predictions.…”

R-parity violating decays of Wino chargino and wino neutralino LSPs and NLSPs at the LHC

“…This could be due, for example, to various non-vanishing F-terms, D-terms or gaugino condensation in the hidden sector of the theory, and is far from unique. Therefore, in this paper and [1,52,53], we simply add to the effective Lagrangian the most general allowed soft supersymmetry breaking terms and choose the values of their parameters statistically. Since the log-uniform distribution is the standard distribution, as justified in Section 2, we will employ it uniquely.…”