Breaking Terms Research Articles

Testing the gaugino AMSB model at the Tevatron via slepton pair production

Gaugino AMSB models — wherein scalar and trilinear soft SUSY breaking terms are suppressed at the GUT scale while gaugino masses adopt the AMSB form — yield a characteristic SUSY particle mass spectrum with light sleptons along with a nearly degenerate wino-like lightest neutralino and quasi-stable chargino. The left-sleptons and sneutrinos can be pair produced at sufficiently high rates to yield observable signals at the Fermilab Tevatron. We calculate the rate for isolated single and dilepton plus missing energy signals, along with the presence of one or two highly ionizing chargino tracks (HITs). We find that Tevatron experiments should be able to probe gravitino masses into the ∼55 TeV range for inoAMSB models (depending on detector-dependent HIT detection efficiency), which corresponds to a reach in gluino mass of over 1100 GeV.

Terms of service, cramped budgets, and good library citizenship: the Netflix dilemma

PurposeThe purpose of this paper is to explore the implications of libraries using Netflix to supplement their own audiovisual collections.Design/methodology/approachA review of the current discussion regarding breaking terms of service is presented along with several complications that arise from libraries disregarding the Netflix terms of service agreement.FindingsThe problem of providing patrons with access to materials that the library cannot afford to purchase and which cannot be acquired via interlibrary loan has no simple answer. Librarians may be in a unique position to encourage changes to terms of service that may be more friendly to lending institutions, but only if they do not squander their legitimacy by disregarding current terms.Research limitations/implicationsMost of the conversation is based on anecdote and recent practice. Very little has been written on how to fix this problem.Practical implicationsThis paper brings this issue to the forefront in an effort to engage librarians in a discussion about the ethical, practical and legal implications of breaking terms of service in the pursuit of serving patrons.Social implicationsThe culture of library practice could be affected by this issue, and may have wider ramifications in terms of future copyright, licensing, and terms of service agreements.Originality/valueThe paper is timely, addressing a current question and debate within their field. It proposes that librarians should find solutions only after seriously considering the legal, ethical, and economic implications of their actions.

Z2index theorem for Majorana zero modes in a classDtopological superconductor

We propose a Z$_2$ index theorem for a generic topological superconductor in class D. Introducing a particle-hole symmetry breaking term depending on a parameter and regarding it as a coordinate of an extra dimension, we define the index of the zero modes and corresponding topological invariant for such an extended Hamiltonian. It is shown that these are related with the number of the zero modes of the original Hamiltonian modulo two.

Direct link between neutrinoless double beta decay and leptogenesis in a seesaw model withS4symmetry

We study how leptogenesis can be implemented in a seesaw model with $S_4$ flavor symmetry, which leads to the neutrino tri-bimaximal mixing matrix and degenerate right-handed (RH) neutrino spectrum. Introducing a tiny soft $S_4$ symmetry breaking term in the RH neutrino mass matrix, we show that the flavored resonant leptogenesis can be successfully realized, which can lower the seesaw scale much so as to make it possible to probe in colliders. Even though such a tiny soft breaking term is essential for leptogenesis, it does not significantly affect the low energy observables. We also investigate how the effective light neutrino mass $|<m_{ee}> |$ associated with neutrinoless double beta decay can be predicted along with the neutrino mass hierarchies by imposing experimental data of low-energy observables. We find a direct link between leptogenesis and neutrinoless double beta decay characterized by $|<m_{ee}>|$ through a high energy CP phase $\phi$, which is correlated with low energy Majorana CP phases. It is shown that our predictions of $|<m_{ee}>|$ for some fixed parameters of high energy physics can be constrained by the current observation of baryon asymmetry.

On non-commutative U⋆(1) gauge models and renormalizability

Based on our recent findings regarding (non-)renormalizability of non-commutative U⋆(1) gauge theories [1, 2] we present the construction of a new type of model. By introducing a soft-breaking term in such a way that only the bilinear part of the action is modified, no interaction between the gauge sector and auxiliary fields occurs. Demanding in addition that the latter form BRST doublet structures, this leads to a minimally altered non-commutative U⋆(1) gauge model featuring an IR damping behavior. Moreover, the new breaking term is shown to provide the necessary structure in order to absorb the inevitable quadratic IR divergences appearing at one-loop level in theories of this kind. In this paper we compute Feynman rules, symmetries and results for the vacuum polarization together with the one-loop renormalization of the gauge boson propagator and three-point functions.

Pseudoscalar mesons in theSU(3)linear sigma model with Gaussian functional approximation

We study the $SU(3)$ linear sigma model for the pseudoscalar mesons in the Gaussian functional approximation (GFA). We use the $SU(3)$ linear sigma model Lagrangian with nonet scalar and pseudoscalar mesons, including symmetry breaking terms. In the GFA, we take the Gaussian Ansatz for the ground state wave function and apply the variational method to minimize the ground state energy. We derive the gap equations for the dressed meson masses, which are actually just variational parameters in the GFA method. We use the Bethe-Salpeter equation for meson-meson scattering, which provides the masses of the physical nonet mesons. We construct the projection operators for the flavor $SU(3)$ in order to work out the scattering $T$ matrix in an efficient way. In this paper, we discuss the properties of the Nambu-Goldstone bosons in various limits of the chiral ${U}_{L}(3)\ifmmode\times\else\texttimes\fi{}{U}_{R}(3)$ symmetry.

Topological phases and phase transitions on the square-octagon lattice

We theoretically investigate a tight binding model of fermions hopping on the square-octagon lattice which consists of a square lattice with plaquette corners themselves decorated by squares. Upon the inclusion of second neighbor spin-orbit coupling or non-Abelian gauge fields, time-reversal symmetric topological Z_2 band insulators are realized. Additional insulating and gapless phases are also realized via the non-Abelian gauge fields. Some of the phase transitions involve topological changes to the Fermi surface. The stability of the topological phases to various symmetry breaking terms is investigated via the entanglement spectrum. Our results enlarge the number of known exactly solvable models of Z_2 band insulators, and are potentially relevant to the realization and identification of topological phases in both the solid state and cold atomic gases.

Supersymmetric dark matter at the LHC 7-TeV run

We have analysed the early LHC signatures of the minimal supergravity (mSUGRA) model. Our emphasis is on the 7 - $TeV$ run corresponding to an integrated luminosity of $\sim 1.0 ~fb^{-1}$ although we have also discussed briefly the prospects at LHC-10 $TeV$. We focus on the parameter space yielding relatively light squark and gluinos consistent with the darkmatter relic density data and the LEP bounds on the lightest Higgs scalar mass. This parameter space is only allowed for non-vanishing trilinear soft breaking term $A_0$. A significant region of the parameter space with large to moderate negative values of $A_0$ consistent with the stability of the scalar potential and relic density production via neutralino annihilation and/or neutralino - stau coannihilation yields observable signal via the jets + missing transverse energy channel. The one lepton + jets + missing energy signal is also viable over a smaller but non-trivial parameter space. The ratio of the size of the two signals - free from theoretical uncertainties - may distinguish between different relic density generating mechanisms. With efficient $\tau$-tagging facilities at 7 $TeV$ the discriminating power may increase significantly. We also comment on other dark matter relic density allowed mSUGRA scenarios and variants there of in the context of LHC-7 $TeV$.

Meson fluctuations and thermodynamics of the Polyakov-loop-extended quark-meson model

Thermodynamics and the phase structure of the Polyakov loop-extended two flavor chiral quark-meson model (PQM) are explored. The analysis of the PQM model is based on the functional renormalization group (FRG) method. An appropriate truncation of the effective action with quarks coupled to background gluonic fields is introduced. Within this scheme, we derive the renormalization group flow equation for the scale-dependent thermodynamic potential at finite temperature and density in the presence of a symmetry breaking external field. The influence of fluctuations and of the background gluon field on the properties of net-quark number density fluctuations and their higher moments is explored. We study the dependence of the kurtosis of quark number fluctuations on the pion mass and show that, in the presence of a symmetry breaking term, the fluctuations lead to a smoothing of observables near the crossover transition.

Meson Properties at Finite Temperature in the Linear Sigma Model

The meson masses are investigated at finite temperature in the framework of the linear sigma model with an explicit chiral symmetry breaking term. The imaginary-time thermo-field dynamics and effective potential have been used for the calculation of the meson masses. We found that the behavior of the sigma and pion masses at finite temperature is in agreement with previous works. The critical temperature, the order of the phase transition, and the dependence of the meson fields on the temperature are discussed.

The soft supersymmetry breaking in [formula omitted] supergravity compactified on [formula omitted] orbifolds

We study the origin of the supersymmetry breaking induced by the mediation of gravity and the radion multiplet from the hidden to the visible brane in the context of the N=2, D=5 supergravity compactified on S1/Z2 orbifolds. The soft supersymmetry breaking terms for scalar masses, trilinear scalar couplings and gaugino masses are calculated to leading order in the five-dimensional Newton's constant k52 and the gravitino mass m3/2. These are finite and non-vanishing, with the scalar soft masses being non-tachyonic, and are all expressed in terms of the gravitino mass and the length scale R of the fifth dimension. The soft supersymmetry breaking parameters are thus correlated and the phenomenological implications are discussed.

Flavoured soft leptogenesis and natural values of the B term

We revisit flavour effects in soft leptogenesis relaxing the assumption of universality for the soft supersymmetry breaking terms. We find that with respect to the case in which the heavy sneutrinos decay with equal rates and equal CP asymmetries for all lepton flavours, hierarchical flavour configurations can enhance the efficiency by more than two orders of magnitude. This translates in more than three order of magnitude with respect to the one-flavour approximation. We verify that lepton flavour equilibration effects related to off-diagonal soft slepton masses are ineffective for damping these large enhancements. We show that soft leptogenesis can be successful for unusual values of the relevant parameters, allowing for $B\sim {\cal O}({\rm TeV})$ and for values of the washout parameter up to $m_{\rm eff}/m_* \sim 5\times 10^{3}$.

Tribimaximal mixing and Cabibbo angle inS4flavor model with supersymmetry

We present a flavor model of quarks and leptons with the non-Abelian discrete symmetry $S_4$ in the framework of the SU(5) SUSY GUT. Three generations of $\bar 5$-plets in SU(5) are assigned to ${\bf 3}$ of $S_4$ while the first and second generations of 10-plets in SU(5) are assigned to ${\bf 2}$ of $S_4$, and the third generation of 10-plet is assigned to ${\bf 1}$ of $S_4$. Right-handed neutrinos are also assigned to ${\bf 2}$ for the first and second generations and ${\bf 1}'$ for the third generation. We predict the Cabibbo angle as well as the tri-bimaximal mixing of neutrino flavors. We also predict the non-vanishing $U_{e3}$ of the neutrino flavor mixing due to higher dimensional mass operators. Our predicted CKM mixing angles and the CP violation are consistent with experimental values. We also study SUSY breaking terms in the slepton sector. Our model leads to smaller values of flavor changing neutral currents than the present experimental bounds.

Moduli redefinitions and moduli stabilisation

Field redefinitions occur in string compactifications at the one loop level. We review arguments for why such redefinitions occur and study their effect on moduli stabilisation and supersymmetry breaking in the LARGE volume scenario. For small moduli, although the effect of such redefinitions can be larger than that of the $\alpha'$ corrections in both the K\"ahler and scalar potentials, they do not alter the structure of the scalar potential. For the less well motivated case of large moduli, the redefinitions can dominate all other terms in the scalar potential. We also study the effect of redefinitions on the structure of supersymmetry breaking and soft terms.

Two-particle correlations in high-energy collisions and the gluon four-point function

We derive the rapidity evolution equation for the gluon four-point function in the dilute regime and at small x from the JIMWLK functional equation. We show that beyond leading order in Nc the mean field (Gaussian) approximation where the four point function is factorized into a product of two point functions is violated. We calculate these factorization breaking terms and show that they contribute at leading order in Nc to correlations of two produced gluons as a function of their relative rapidity and azimuthal angle, for generic (rather than back-to-back) angles. Such two-particle correlations have been studied experimentally at the BNL-RHIC collider and could be scrutinized also for pp (and, in the future, also AA) collisions at the CERN-LHC accelerator.

One-Loop Calculations and Detailed Analysis of the Localized Non-Commutative p-2U(1) Gauge Model

This paper carries forward a series of articles describing our enterprise to construct a gauge equivalent for the $\theta$-deformed non-commutative $p^{-2}$ model originally introduced by Gurau et al. arXiv:0802.0791. It is shown that breaking terms of the form used by Vilar et al. arXiv:0902.2956 and ourselves arXiv:0901.1681 to localize the BRST covariant operator $(D^2\theta^2D^2)^{-1}$ lead to difficulties concerning renormalization. The reason is that this dimensionless operator is invariant with respect to any symmetry of the model, and can be inserted to arbitrary power. In the present article we discuss explicit one-loop calculations, and analyze the mechanism the mentioned problems originate from.

Orbifolds, fuzzy spheres and chiral fermions

Starting with a N=4 supersymmetric Yang-Mills theory in four dimensions with gauge group SU(3N) we perform an orbifold projection leading to a N=1 supersymmetric SU(N)^3 Yang-Mills theory with matter supermultiplets in bifundamental representations of the gauge group, which is chiral and anomaly free. Subsequently, we search for vacua of the projected theory which can be interpreted as spontaneously generated twisted fuzzy spheres. We show that by adding the appropriate soft supersymmetry breaking terms we can indeed reveal such vacua. Three cases are studied, where the gauge group is spontaneously broken further to the low-energy gauge groups SU(4)xSU(2)xSU(2), SU(4)^3 and SU(3)^3. Such models behave in intermediate scales as higher-dimensional theories with a finite Kaluza-Klein tower, while their low-energy physics is governed by the corresponding zero-modes and exhibit chirality in the fermionic sector. The most interesting case from the phenomenological point of view turns out to be the SU(3)^3 unified theory, which has several interesting features such as (i) it can be promoted to a finite theory, (ii) it breaks further spontaneously first to the MSSM and then to SU(3)xU(1)_{em} due to its own scalar sector, i.e. without the need of additional superfields and (iii) the corresponding vacua lead to spontaneously generated fuzzy spheres.

Gaugino anomaly mediated SUSY breaking: phenomenology and prospects for the LHC

We examine the supersymmetry phenomenology of a novel scenario of supersymmetry (SUSY) breaking which we call Gaugino Anomaly Mediation, or inoAMSB. This is suggested by recent work on the phenomenology of flux compactified type IIB string theory. The essential features of this scenario are that the gaugino masses are of the anomaly-mediated SUSY breaking (AMSB) form, while scalar and trilinear soft SUSY breaking terms are highly suppressed. Renormalization group effects yield an allowable sparticle mass spectrum, while at the same time avoiding charged LSPs; the latter are common in models with negligible soft scalar masses, such as no-scale or gaugino mediation models. Since scalar and trilinear soft terms are highly suppressed, the SUSY induced flavor and CP-violating processes are also suppressed. The lightest SUSY particle is the neutral wino, while the heaviest is the gluino. In this model, there should be a strong multi-jet +etmiss signal from squark pair production at the LHC. We find a 100 fb^{-1} reach of LHC out to m_{3/2}\sim 118 TeV, corresponding to a gluino mass of \sim 2.6 TeV. A double mass edge from the opposite-sign/same flavor dilepton invariant mass distribution should be visible at LHC; this, along with the presence of short-- but visible-- highly ionizing tracks from quasi-stable charginos, should provide a smoking gun signature for inoAMSB.

A see-saw S4 model for fermion masses and mixings

We present a supersymmetric see-saw S4 model giving rise to the most general neutrino mass matrix compatible with tri-bimaximal mixing. We adopt the S4 × Z5 flavour symmetry, broken by suitable vacuum expectation values of a small number of flavon fields. We show that the vacuum alignment is a natural solution of the most general superpotential allowed by the flavour symmetry, without introducing any soft breaking terms. In the charged lepton sector, mass hierarchies are controlled by the spontaneous breaking of the flavour symmetry caused by the vevs of one doublet and one triplet flavon fields instead of using the Froggatt–Nielsen U(1) mechanism. The next to leading order corrections to both charged lepton mass matrix and flavon vevs generate corrections to the mixing angles as large as . Applied to the quark sector, the symmetry group S4 × Z5 can give a leading order VCKM proportional to the identity as well as a matrix with coefficients in the Cabibbo 2 × 2 submatrix. Higher order corrections produce nonvanishing entries in the other VCKM entries which are generically of .

Minimal supersymmetric hybrid inflation, flipped [formula omitted] and proton decay

Minimal supersymmetric hybrid inflation utilizes a canonical Kähler potential and a renormalizable superpotential which is uniquely determined by imposing a U(1) R-symmetry. In computing the scalar spectral index ns we take into account modifications of the tree level potential caused by radiative and supergravity corrections, as well as contributions from the soft supersymmetry breaking terms with a negative soft mass-squared term allowed for the inflaton. All of these contributions play a role in realizing ns values in the range 0.96–0.97 preferred by WMAP. The U(1) R-symmetry plays an important role in flipped SU(5) by eliminating the troublesome dimension five proton decay. The proton decays into e+π0 via dimension six operators arising from the exchange of superheavy gauge bosons with a lifetime of order 1034–1036 years.