Scalar Multiplets Research Articles

Phenomenology of left-right symmetric dark matter

We present a detailed study of dark matter phenomenology in low-scale left-right symmetric models. Stability of new fermion or scalar multiplets is ensured by an accidental matter parity that survives the spontaneous symmetry breaking of the gauge group by scalar triplets. The relic abundance of these particles is set by gauge interactions and gives rise to dark matter candidates with masses above the electroweak scale. Dark matter annihilations are thus modified by the Sommerfeld effect, not only in the early Universe, but also today, for instance, in the Center of the Galaxy. Majorana candidates—triplet, quintuplet, bi-doublet, and bi-triplet—bring only one new parameter to the model, their mass, and are hence highly testable at colliders and through astrophysical observations. Scalar candidates—doublet and 7-plet, the latter being only stable at the renormalizable level—have additional scalar-scalar interactions that give rise to rich phenomenology. The particles under discussion share many features with the well-known candidates wino, Higgsino, inert doublet scalar, sneutrino, and Minimal Dark Matter. In particular, they all predict a large gamma-ray flux from dark matter annihilations, which can be searched for with Cherenkov telescopes. We furthermore discuss models with unequal left-right gauge couplings, gR ≠ gL, taking the recent experimental hints for a charged gauge boson with 2 TeV mass as a benchmark point. In this case, the dark matter mass is determined by the observed relic density.

Implications of the CMS search for W R on grand unification

The CMS experiment at the Large Hadron Collider has reported a 2.8$\sigma$ excess in the $(2e)(2jets)$ channel around 2.1 TeV. Interpretation of this data is reconsidered in terms of the production of a right-handed weak gauge boson, $W_R$, of the left-right symmetric model and in an $SO(10)$ grand unified theory abiding by the Extended Survival Hypothesis. The left-right symmetric model can be consistent with this excess if (a) the heavy right-handed neutrino has a mass near $W_R$, or (b) if $g_L \neq g_R$, or (c) the right-handed CKM matrix is nontrivial. Combinations of the above possibilities are also viable. A $W_R$ with a mass in the TeV region if embedded in $SO(10)$ is not compatible with $g_L = g_R$. Rather, it implies $0.64 \leq g_R/g_L \leq 0.78$. Further, a unique symmetry-breaking route -- the order being left-right discrete symmetry breaking first, followed by $SU(4)_C$ and finally $SU(2)_R$ -- to the standard model is picked out. The $L \leftrightarrow R$ discrete symmetry has to be broken at around $10^{16}$ GeV. The grand unification scale is pushed to $10^{18}$ GeV making the detection of proton decay in ongoing searches rather unlikely. The $SU(4)_C$ breaking scale can be at its allowed lower limit of $10^6$ GeV so that $n - \bar{n}$ oscillation or flavour changing processes such as $K_L \rightarrow \mu e$ and $B_{d,s} \rightarrow \mu e$ may be detectable. The Higgs scalar multiplets responsible for $SO(10)$ symmetry breaking at various stages are uniquely identified so long as one adheres to a minimalist principle. We also remark, {\em en passant}, about a partially unified Pati-Salam model.

Scalar sector phenomenology of three-loop radiative neutrino mass models

We perform a phenomenological study of the scalar sector of two models that generate neutrino mass at the three-loop level and contain viable dark matter candidates. Both models contain a charged singlet scalar and a larger scalar multiplet (triplet or quintuplet). We investigate the effect of the extra scalars on the Higgs mass and analyze the modifications to the triple Higgs coupling. The new scalars can give observable changes to the Higgs decay channel $h\rightarrow\gamma \gamma$ and, furthermore, we find that the electroweak phase transition becomes strongly first-order in large regions of parameter space.

Band-selective excited ultrahigh resolution PSYCHE-TOCSY: fast screening of organic molecules and complex mixtures.

Precise assignments of (1) H atomic sites and establishment of their through-bond COSY or TOCSY connectivity are crucial for molecular structural characterization by using (1) H NMR spectroscopy. However, this exercise is often hampered by signal overlap, primarily because of (1) H-(1) H scalar coupling multiplets, even at typical high magnetic fields. The recent developments in homodecoupling strategies for effectively suppressing the coupling multiplets into nice singlets (pure-shift), particularly, Morris's advanced broadband pure-shift yielded by chirp excitation (PSYCHE) decoupling and ultrahigh resolution PSYCHE-TOCSY schemes, have shown new possibilities for unambiguous structural elucidation of complex organic molecules. The superior broadband PSYCHE-TOCSY exhibits enhanced performance over the earlier TOCSY methods, which however warrants prolonged experimental times due to the requirement of large number of dwell increments along the indirect dimension. Herein, we present fast and band-selective analog of the broadband PSYCHE-TOCSY, which is useful for analyzing complex organic molecules that exhibit characteristic yet crowded spectral regions. The simple pulse scheme relies on band-selective excitation (BSE) followed by PSYCHE homodecoupling in the indirect dimension. The BSE-PSYCHE-TOCSY has been exemplified for Estradiol and a complex carbohydrate mixture comprised of six constituents of closely comparable molecular weights. The experimental times are greatly reduced viz., ~20 fold for Estradiol and ~10 fold for carbohydrate mixture, with respect to the broadband PSYCHE-TOCSY. Furthermore, unlike the earlier homonuclear band-selective decoupling, the BSE-PSYCHE-decoupling provides fully decoupled pure-shift spectra for all the individual chemical sites within the excited band. The BSE-PSYCHE-TOCSY is expected to have significant potential for quick screening of complex organic molecules and mixtures at ultrahigh resolution. Copyright © 2015 John Wiley & Sons, Ltd.

Quark Yukawa pattern from spontaneous breaking of flavour [formula omitted

A SU(3)Q×SU(3)u×SU(3)d invariant scalar potential breaking spontaneously the quark flavour symmetry can explain the Standard Model flavour puzzle. The approximate alignment in flavour space of the vacuum expectation values of the up and down ‘Yukawa fields’ results as a dynamical effect. The observed quark mixing angles, the weak CP violating phase, and hierarchical quark masses can be all reproduced at the cost of introducing additional (auxiliary) scalar multiplets, but without the need of introducing hierarchical parameters.

LHC constraints on large scalar multiplet models with aZ2symmetry

We study the LHC search constraints on models that extend the Standard Model with an inert, complex scalar electroweak multiplet, $\mathrm{\ensuremath{\Sigma}}$, with isospin $T=5/2$ (sextet) or $T=7/2$ (octet) and identical hypercharge to the Standard Model Higgs doublet. Imposing a global ${Z}_{2}$ symmetry under which $\mathrm{\ensuremath{\Sigma}}\ensuremath{\rightarrow}\ensuremath{-}\mathrm{\ensuremath{\Sigma}}$, the lightest member of $\mathrm{\ensuremath{\Sigma}}$ is stable, and we require that it be neutral (${\ensuremath{\zeta}}^{0,r}$) to avoid cosmological constraints from charged relics. Pair production of scalars by electroweak interactions followed by cascade decays to ${\ensuremath{\zeta}}^{0,r}$ through $W$ and $Z$ emission produces signatures similar to those of supersymmetric electroweak gauginos, and we constrain the models by recasting a collection of such searches made with data from the 8 TeV run of the LHC. We find that there is no sensitivity from these searches to the compressed spectrum regime, in which the mass splittings between the lightest and heaviest states in $\mathrm{\ensuremath{\Sigma}}$ are less than about 20 GeV. In the remaining parameter space, we find significant exclusions for ${m}_{{\ensuremath{\zeta}}^{0,r}}\ensuremath{\sim}80--180\text{ }\text{ }\mathrm{GeV}$ in the sextet model, and ${m}_{{\ensuremath{\zeta}}^{0,r}}\ensuremath{\sim}80--120\text{ }\text{ }\mathrm{GeV}$ in the octet model.

Non-minimal scalar multiplets, supersymmetry breaking and dualities

We study supersymmetry breaking in theories with non-minimal multiplets (such as the complex linear or CNM multiplets), by using superspace higher derivative terms which give rise to new supersymmetry breaking vacuum solutions on top of the standard supersymmetric vacuum. We illustrate the decoupling of the additional massive sectors inside the complex linear and the CNM multiplets and show that only the Goldstino sector is left in the low energy limit. We also discuss the duality between non-minimal scalar multiplets and chiral multiplets in the presence of superspace higher derivatives. From the superspace Noether procedure we calculate the supercurrents, and we show that in the supersymmetry breaking vacuum the chiral superfield X which enters the Ferrara-Zumino supercurrent conservation equation does indeed flow in the IR to the chiral constrained Goldstino superfield. We also provide a description of the Goldstino sector in terms of the Samuel-Wess superfield for the supersymmetry breaking mechanism at hand.

Minimal asymmetric dark matter

In the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle–antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM) with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic) SU(2)L multiplet χ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between χ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, leaving as the only possibilities scalar or fermion multiplets with hypercharge y=1, preferentially quintuplets or larger SU(2) representations, and with a mass in the few TeV range.

Extended Jackiw–Pi model and its supersymmetrization

We present an extended version of the so-called Jackiw–Pi (JP) model in three dimensions, and perform its supersymmetrization. Our field content has three multiplets: (i) Yang–Mills vector multiplet (AμI,λI), (ii) Parity-odd extra vector multiplet (BμI,χI), and (iii) Scalar multiplet (CI,ρI;fI). The bosonic fields in these multiplets are the same as the original JP-model, except for the auxiliary field fI which is new, while the fermions λI, χI and ρI are their super-partners. The basic difference from the original JP-model is the presence of the kinetic term for CI with its modified field-strength HμI≡DμCI+mBμI. The inclusion of the CI-kinetic term is to comply with the recently-developed tensor hierarchy formulation for supersymmetrization.

Existence of static dyonic black holes in 4d N = 1 supergravity with finite energy

We prove the existence and the uniqueness of the static dyonic black holes in four dimensional N = 1 supergravity theory coupled vector and scalar multiplets. We set the near-horizon geometry to be a product of two Einstein surfaces, whereas the asymptotic geometry has to be a space of constant scalar curvature. Using these data, we show that there exists a unique solution for scalar fields which interpolates these regions.

Massive N $$ \mathcal{N} $$ = 2 supergravity in three dimensions

There exists two distinct off-shell ${\mathcal{N}}=2$ supergravities in three dimensions. They are also referred to as ${\mathcal{N}}=(1,1)$ and ${\mathcal{N}}=(2,0)$ supergravities, and they arise from the coupling of the Weyl multiplet to a compensating scalar or vector multiplet, respectively, followed by fixing of conformal symmetries. The ${\mathcal{N}} =(p,q)$ terminology refers to the underlying anti-de Sitter superalgebras $OSp(2,p) \oplus OSp(2,q)$ with $R$-symmetry group $SO(p) \times SO(q)$. We construct off-shell invariants of these theories up to fourth order in derivatives. As an application of these results, we determine the special combinations of the ${\mathcal{N}}=(1,1)$ invariants that admit anti-de Sitter vacuum solution about which there is a ghost-free massive spin-2 multiplet of propagating modes. We also show that the ${\mathcal{N}}=(2,0)$ invariants do not allow such possibility.

Supergravity one-loop corrections on AdS7 and AdS3, higher spins and AdS/CFT

As was shown earlier, the one-loop correction in 10d supergravity on AdS5×S5 corresponds to the contributions to the vacuum energy and 4d boundary conformal anomaly which are minus the values for one N=4 Maxwell supermultiplet, thus reproducing the subleading term in the N2−1 coefficient in the dual SU(N) SYM theory. We perform similar one-loop computations in 11d supergravity on AdS7×S4 and 10d supergravity on AdS3×S3×T4. In the AdS7 case we find that the corrections to the 6d conformal anomaly a-coefficient and the vacuum energy are again minus the ones for one (2,0) tensor multiplet, suggesting that the total a-anomaly coefficient for the dual (2,0) theory is 4N3−9/4N−7/4 and thus vanishes for N=1. In the AdS3 case the one-loop correction to the vacuum energy or 2d central charge turns out to be equal to that of one free (4,4) scalar multiplet, i.e. is c=+6. This reproduces the subleading term in the central charge c=6(Q1Q5+1) of the dual 2d CFT describing decoupling limit of D5–D1 system. We also present the expressions for the 6d a-anomaly coefficient and vacuum energy contributions of general-symmetry higher spin field in AdS7 and consider their application to tests of vectorial AdS/CFT with the boundary conformal 6d theory represented by free scalars, spinors or rank-2 antisymmetric tensors.

Sphalerons and the electroweak phase transition in models with higher scalar representations

In this work we investigate the sphaleron solution in a $SU(2)\times U(1)_X$ gauge theory, which also encompasses the Standard Model, with higher scalar representation(s) ($J^{(i)},X^{(i)}$). We show that the field profiles describing the sphaleron in higher scalar multiplet, have similar trends like the doublet case with respect to the radial distance. We compute the sphaleron energy and find that it scales linearly with the vacuum expectation value of the scalar field and its slope depends on the representation. We also investigate the effect of $U(1)$ gauge field and find that it is small for the physical value of the mixing angle, $\theta_{W}$ and resembles the case for the doublet. For higher representations, we show that the criterion for strong first order phase transition, $v_{c}/T_{c}>\eta$, is relaxed with respect to the doublet case, i.e. $\eta<1$.

A possible 130 GeV gamma‐ray line from annihilating singlet fermionic dark matter

AbstractThere is evidence for a spectral line at Eγ ≈ 130 GeV in the Fermi ‐LAT data that can be explained as dark mater particles annihilating into photons. We review a well known dark matter model that consists in a singlet Dirac fermion and a singlet scalar. The scalar implements spontaneous symmetry breaking in the dark sector, and is responsible for the communication between dark matter and standard model particles through a coupling to the Higgs. These interactions are suppressed by the mixing between the scalar and the Higgs. Therefore, the singlet fermionic dark matter is naturally a weakly interacting massive particle (WIMP) and can explain the observed relic density. We show that this model cannot produce the signal identified in the Fermi ‐LAT data. Thus, we propose a modification in the model by introducing a new scalar multiplet that carries electric charge and couples to the singlet scalar. It enhances the annihilation into two photons and succeeds in producing the observed signal. We also discuss the resulting increase of the branching ratio of the h → γγ process, which is consistent with measurements from the CMS experiments. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

RG flows in 6D N = (1,0) SCFT from SO(4) half-maximal 7D gauged supergravity

We study $N=2$ seven-dimensional gauged supergravity coupled to three vector multiplets with $SO(4)$ gauge group. The resulting gauged supergravity contains 10 scalars consisting of the dilaton and 9 vector multiplet scalars parametrized by $SO(3,3)/SO(3)\times SO(3)$ coset manifold. The maximally supersymmetric $AdS_7$ vacuum with unbroken $SO(4)$ symmetry is identified with a $(1,0)$ SCFT in six dimensions. We find one new supersymmetric $AdS_7$ critical point preserving $SO(3)_{\textrm{diag}}\subset SO(3)\times SO(3)\sim SO(4)$ and study a holographic RG flow interpolating between the $SO(4)$ and the new $SO(3)$ supersymmetric critical points. The RG flow is driven by a vacuum expectation value of a dimension-four operator and describes a deformation of the UV $(1,0)$ SCFT to another supersymmetric fixed point in the IR. In addition, a number of non-supersymmetric critical points are identified, and some of them are stable with all scalar masses above the BF bound. RG flows to non-conformal $N=(1,0)$ Super Yang-Mills with $SO(2)\times SO(2)$ and $SO(2)$ symmetries are also investigated. Some of these flows have physically acceptable IR singularities since the scalar potential is bounded above. These provide physical RG flows from $(1,0)$ SCFT to non-conformal field theories in six dimensions.

Resonance effects in pion and kaon decay constants

In this article we study impact of the lightest vector and scalar resonance multiplets in the pion and kaon decay constants up to next-to-leading order in the $1/N_C$ expansion, i.e., up to the one-loop level. The $F_\pi$ and $F_K$ predictions obtained within the framework of Resonance Chiral Theory are confronted with lattice simulation data. The vector loops (and the $\rho-\pi\pi$ coupling $G_V$ in particular) are found to play a crucial role in the determination of the Chiral Perturbation Theory couplings $L_4$ and $L_5$ at next-to-leading order in $1/N_C$. Puzzling, values of $G_V < 40$ MeV seem to be necessary to agree with current phenomenological results for $L_4$ and $L_5$. Conversely, a value of $G_V > 60$ MeV compatible with standard $\rho-\pi\pi$ determinations turns these chiral couplings negative. However, in spite of the strong anti-correlation with $L_4$, the $SU(3)$ chiral coupling $F_0$ remains stable all the time and stays within the range $78 \sim 86$ MeV when $G_V$ is varied in a wide range, from $40$ up to $70$ MeV. Finally, we would like to remark that the leading order expressions used in this article for the $\eta-\eta'$ mixing, mass splitting of the vector multiplet masses and the quark mass dependence of the $\rho(770)$ mass are found in reasonable agreement with the lattice data.

Real-time homonuclear broadband and band-selective decoupled pure-shift ROESY.

Unambiguous spectral assignments in (1)H solution-state NMR are central, for accurate structural elucidation of complex molecules, which is often hampered by signal overlap, primarily because of scalar coupling multiplets, even at typical high magnetic fields. The recent advances in homodecoupling methods have shown powerful means of achieving high resolution pure-shift (1)H spectra in 1D and also in 2D J-correlated experiments, by effectively collapsing the multiplet structures. The present work extends these decoupling strategies to through-space correlation experiments as well and describes two new pure-shift ROESY pulse schemes with homodecoupling during acquisition, viz., homodecoupled broadband (HOBB)-ROESY and homodecoupled band-selective (HOBS)-ROESY. Furthermore, the ROESY blocks suppress the undesired interferences of TOCSY cross peaks and other offsets. Despite the reduced signal sensitivity and prolonged experimental times, the HOBB-ROESY is particularly useful for molecules that exhibit an extensive scalar coupling network spread over the entire (1)H chemical shift range, such as natural/synthetic organic molecules. On the other hand, the HOBS-ROESY is useful for molecules that exhibit well-separated chemical shift regions such as peptides (NH, Hα and side-chain protons). The HOBS-ROESY sensitivities are comparable with the conventional ROESY, thereby saves the experimental time significantly. The power of these pure-shift ROESY sequences is demonstrated for two different organic molecules, wherein complex conventional ROE cross peaks are greatly simplified with high resolution and sensitivity. The enhanced resolution allows deriving possibly more numbers of ROEs with better accuracy, thereby facilitating superior means of structural characterization of medium-size molecules.

Supersymmetry breaking by higher dimension operators

We discuss a supersymmetry breaking mechanism for N=1 theories triggered by higher dimensional operators. We consider such operators for real linear and chiral spinor superfields that break supersymmetry and reduce to the Volkov–Akulov action. We also consider supersymmetry breaking induced by a higher dimensional operator of a nonminimal scalar (complex linear) multiplet. The latter differs from the standard chiral multiplet in its auxiliary sector, which contains, in addition to the complex scalar auxiliary of a chiral superfield, a complex vector and two spinors auxiliaries. By adding an appropriate higher dimension operator, the scalar auxiliary may acquire a nonzero vev triggering spontaneous supersymmetry breaking. We find that the spectrum of the theory in the supersymmetry breaking vacuum consists of a free chiral multiplet and a constraint chiral superfield describing the goldstino. Interestingly, the latter turns out to be one of the auxiliary fermions, which becomes dynamical in the supersymmetry breaking vacuum. In all cases we are considering here, there is no sgoldstino mode and thus the goldstino does not have a superpartner. The sgoldstino is decoupled since the goldstino is one of the auxiliaries, which is propagating only in the supersymmetry breaking vacuum. We also point out how higher dimension operators introduce a potential for the propagating scalar of the theory.

Nonabelian dark matter with resonant annihilation

We construct a model based on an extra gauge symmetry, SU(2)_X x U(1)_{B-L}, which can provide gauge bosons to serve as weakly-interacting massive particle dark matter. The stability of the dark matter is naturally guaranteed by a discrete Z_2 symmetry that is a subgroup of SU(2)_X. The dark matter interacts with standard model fermions by exchanging gauge bosons which are linear combinations of SU(2)_X x U(1)_{B-L} gauge bosons. With the appropriate choice of representation for the new scalar multiplet whose vacuum expectation value spontaneously breaks the SU(2)_X symmetry, the relation between the new gauge boson masses can naturally lead to resonant pair annihilation of the dark matter. After exploring the parameter space of the new gauge couplings subject to constraints from collider data and the observed relic density, we use the results to evaluate the cross section of the dark matter scattering off nucleons and compare it with data from the latest direct detection experiments. We find allowed parameter regions that can be probed by future direct searches for dark matter and LHC searches for new particles.

Vacuum structure in a chiral [formula omitted] modification of pure supergravity

We discuss an R+Rn class of modified N=1, D=4 supergravity models where the deformation is a monomial Rn|F in the chiral scalar curvature multiplet R of the “old minimal” auxiliary field formulation. The scalaron and goldstino multiplets are dual to each other in this theory. Since one of them is not dynamical, this theory, as recently shown, cannot be used as the supersymmetric completion of R+Rn gravity. This is confirmed by investigating the scalar potential and its critical points in the dual standard supergravity formulation with a single chiral multiplet with specific Kähler potential and superpotential. We study the vacuum structure of this dual theory and we find that there is always a supersymmetric Minkowski critical point which however is pathological for n⩾3 as it corresponds to a corner (n=3) and a cusp (n>3) point of the potential. For n>3 an anti-de Sitter regular supersymmetric vacuum emerges. As a result, this class of models are not appropriate to describe inflation. We also find the mass spectrum and we provide a general formula for the masses of the scalars of a chiral multiplet around the anti-de Sitter critical point and their relation to osp(1,4) unitary representations.