arXiv subjects

V. E. Mayes

Publications and source records attributed to V. E. Mayes.

11 recordsLinked to original sources

arXiv2008

Yukawa Corrections from Four-Point Functions in Intersecting D6-Brane Models

We discuss corrections to the Yukawa matrices of the Standard Model (SM) fermions in intersecting D-brane models due to four-point interactions. Recently, an intersecting D-brane model has been found where it is possible to obtain correct masses and mixings for all quarks as well as the tau lepton. However, the masses for the first two charged leptons come close to the right values but are not quite correct. Since the electron and muon are quite light, it is likely that there are additional corrections to their masses which cannot be neglected. With this in mind, we consider contributions to the SM fermion mass matrices from four-point interactions. In an explicit model, we show that it is indeed possible to obtain the SM fermion masses and mixings which are a better match to those resulting from experimental data extrapolated at the unification scale when these corrections are included. These corrections may have broader application to other models.

hep-th↗

arXiv2008

Realistic Yukawa Textures and SUSY Spectra from Intersecting Branes

We study the possible phenomenology of a three-family Pati-Salam model constructed from intersecting D6-branes in Type IIA string theory on the T^6/(Z2 x Z2) orientifold with some desirable semi-realistic features. In the model, tree-level gauge coupling unification is achieved automatically at the string scale, and the gauge symmetry may be broken to the Standard Model (SM) close to the string scale. The small number of extra chiral exotic states in the model may be decoupled via the Higgs mechanism and strong dynamics. We calculate the possible supersymmetry breaking soft terms and the corresponding low-energy supersymmetric particle spectra which may potentially be tested at the Large Hadron Collider (LHC). We find that for the viable regions of the parameter space the lightest CP-even Higgs boson mass usually satisfies m_H < 120 GeV, and the observed dark matter density may be generated. Finally, we find that it is possible to obtain correct SM quark masses and mixings, and the tau lepton mass at the unification scale. Additionally, neutrino masses and mixings may be generated via the seesaw mechanism. Mechanisms to stabilize the open and closed-string moduli, which are necessary for the model to be truly viable and to make definite predictions are discussed.

hep-ph↗

arXiv2007

Variations of the Hidden Sector in a Realistic Intersecting Brane Model

Recently, we discussed the first example of a phenomenologically realistic intersecting D6-brane model. In this model, the gauge symmetry in the hidden sector is USp(2)_1 x USp(2)_2 x USp(2)_3 x USp(2)_4. However, we find that the USp(2)_1 x USp(2)_2 gauge symmetry can be replaced by an U(2)_{12} gauge symmetry, and/or the USp(2)_3 x USp(2)_4 gauge symmetry can be replaced by an U(2)_{34} gauge symmetry since the USp(2)^2 stacks of D6-branes contribute to the same Ramond-Ramond tadpoles as those of the U(2) stacks. Thus, there are three non-equivalent variations of the hidden sector, and the corresponding gauge symmetries are U(2)_{12} x USp(2)_3 x USp(2)_4, U(2)_{34} x USp(2)_1 x USp(2)_2, and U(2)_{12} x U(2)_{34}, respectively. Moreover, we study the hidden sector gauge symmetry breaking, discuss how to decouple the additional exotic particles, and briefly comment on the phenomenological consequences.

hep-th↗

arXiv2007

A Realistic World from Intersecting D6-Branes

We briefly describe a three-family intersecting D6-brane model in Type IIA theory on the T^6/(Z_2 x Z_2) orientifold with a realistic phenomenology. In this model, the gauge symmetry can be broken down to the Standard Model (SM) gauge symmetry close to the string scale, and the gauge coupling unification can be achieved. We calculate the supersymmetry breaking soft terms, and the corresponding low energy supersymmetric particle spectrum, which may be tested at the Large Hadron Collider (LHC). The observed dark matter density may also be generated. Finally, we can explain the SM quark masses and CKM mixings, and the tau lepton mass. The neutrino masses and mixings may be generated via the seesaw mechanism as well.

hep-th↗

arXiv2007

MSSM via Pati-Salam from Intersecting Branes on $T^6/(\mathbf{\Z_2} \times \mathbf{\Z_2'})$

We construct an MSSM-like model via Pati-Salam from intersecting D-branes in Type IIA theory on the $\Z_2 \times \Z_2'$ orientifold where the D-branes wrap rigid 3-cycles. Because the 3-cycles are rigid, there are no extra massless fields in the adjoint representation, arising as open-string moduli. The presence of these unobserved fields would create difficulties with asymptotic freedom as well as the prediction of gauge unification. The model constructed has four generations of MSSM matter plus right-handed neutrinos, as well as additional vector-like representations. In addition, we find that all of the required Yukawa couplings are allowed by global symmetries which arise from U(1)'s which become massive via a generalized Green-Schwarz mechanism. Furthermore, we find that the tree-level gauge couplings are unified at the string scale.

hep-th↗

arXiv2006

UHECR Particle Spectra from Crypton Decays

We calculate the spectra of ultra-high-energy cosmic rays (UHECRs) in an explicit top-down model based on the decays of metastable neutral `crypton' states in a flipped SU(5) string model. For each of the eight specific 10th-order superpotential operators that might dominate crypton decays, we calculate the spectra of both protons and photons, using a code incorporating supersymmetric evolution of the injected spectra. For all the decay operators, the total UHECR spectra are compatible with the available data. Also, the fractions of photons are compatible with all the published upper limits, but may be detectable in future experiments.

astro-ph↗

arXiv2005

Flipped SU(5) From D-branes With Type IIB Fluxes

We construct flipped SU(5) GUT models as Type IIB flux vacua on $\Z_2\times \Z_2$ orientifolds. Turning on supergravity self-dual NSNS and RR three-form fluxes fixes the toroidal complex structure moduli and the dilaton. We give a specific example of a three-generation flipped SU(5) model with a complete Higgs sector where supersymmetry is softly broken by the supergravity fluxes in the closed string sector. All of the required Yukawa couplings are present if global U(1) factors resulting from a generalized Green-Schwarz mechanism are broken spontaneously or by world-sheet instantons. In addition, the model contains extra chiral and vector-like matter, potentially of mass $\mathcal{O}(M_{string})$ via trilinear superpotential couplings.

hep-th↗

arXiv2005

A K-theory Anomaly Free Supersymmetric Flipped SU(5) Model from Intersecting Branes

We construct an N=1 supersymmetric three-family flipped SU(5) model from type IIA orientifolds on $T^6/(\Z_2\times \Z_2)$ with D6-branes intersecting at general angles. The model is constrained by the requirement that Ramond-Ramond tadpoles cancel, the supersymmetry conditions, and that the gauge boson coupled to the $U(1)_X$ factor does not get a string-scale mass via a generalised Green-Schwarz mechanism. The model is further constrained by requiring cancellation of K-theory charges. The spectrum contains a complete grand unified and electroweak Higgs sector, however the latter in a non-minimal number of copies. In addition, it contains extra matter both in bi-fundamental and vector-like representations as well as two copies of matter in the symmetric representation of SU(5).

hep-th↗

arXiv2005

A Supersymmetric Flipped SU(5) Intersecting Brane World

We construct an N=1 supersymmetric three-family flipped SU(5) model from type IIA orientifolds on $T^6/(\Z_2\times \Z_2)$ with D6-branes intersecting at general angles. The spectrum contains a complete grand unified and electroweak Higgs sector. In addition, it contains extra exotic matter both in bi-fundamental and vector-like representations as well as two copies of matter in the symmetric representation of SU(5).

hep-th↗

arXiv2004

Flipped Cryptons and the UHECRs

Cryptons are metastable bound states of fractionally-charged particles that arise generically in the hidden sectors of models derived from heterotic string. We study their properties and decay modes in a specific flipped SU(5) model with long-lived four-particle spin-zero bound states called {\it tetrons}. We show that the neutral tetrons are metastable, and exhibit the tenth-order non-renormalizable superpotential operators responsible for their dominant decays. By analogy with QCD, we expect charged tetrons to be somewhat heavier, and to decay relatively rapidly via lower-order interactions that we also exhibit. The expected masses and lifetimes of the neutral tetrons make them good candidates for cold dark matter (CDM), and a potential source of the ultra-high energy cosmic rays (UHECRs) which have been observed, whereas the charged tetrons would have decayed in the early Universe.

hep-ph↗

arXiv2003

High Precision Measurement of the Superallowed 0^+ to 0^+ Beta Decay of ^{22}Mg

The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12), for ^{22}Mg beta-decay have been measured with high precision. The latter depended on gamma-ray intensities being measured with an HPGe detector calibrated for relative efficiencies to an unprecedented 0.15%. Previous precise measurements of 0^+ to 0^+ transitions have been restricted to the nine that populate stable daughter nuclei. No more such cases exist, and any improvement in a critical CKM unitarity test must depend on precise measurements of more exotic nuclei. With this branching-ratio measurement, we show those to be possible for T_z = -1 parents. We obtain a corrected Ft-value of 3071(9) s, in good agreement with expectations.

nucl-ex↗