We propose an extension to the Standard Model accommodating two families of Dirac neutral fermions and Majorana fermions under additional ${U(1)_{e-μ} \times Z_3\times Z_2}$ symmetries where ${U(1)_{e-μ}}$ is a flavor dependent gauge symmetry related to the first and second family of the lepton sector, which features a two-loop induced neutrino mass model. The two families are favored by minimally reproducing the current neutrino oscillation data and two mass difference squares and canceling the gauge anomalies at the same time. As a result, we have a prediction for neutrino masses. The lightest Dirac neutral fermion is a dark matter candidate with tree-level interaction restricted to electron, muon and neutrinos, which makes it difficult to detect in direct dark matter search as well as indirect search focusing on the $τ$-channel, such as through $γ$-rays. It may however be probed by search for dark matter signatures in electron and positron cosmic rays, and allows interpretation of a structure appearing in the CALET electron+positron spectrum around 350-400 GeV as its signature, with a boost factor $\approx$40 Breit-Wigner enhancement of the annihilation cross section.
The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lept…
Within the standard propagation scenario, the flavor ratios of high-energy cosmic neutrinos at neutrino telescopes are expected to be around the democratic benchmark resulting from hadronic sources, $\left( 1 : 1 : 1 \right)_\oplus$. We show how the coupling of neutrinos to an ultralight dark matter complex scalar field would induce an effective neutrino mass that could lead to adiabatic neutrino propagation. This would result in the preservation at the detector of the production flavor composition of neutrinos at sources. This effect could lead to flavor ratios at detectors well outside the r…
We show how cosmic gamma rays can be used to constrain models of asymmetric Dark Matter decaying into lepton pairs by violating flavor. First of all we require the models to explain the anomalies in the charged cosmic rays measured by PAMELA, FERMI and HESS; performing combined fits we determine the allowed values of the Dark Matter mass and lifetime. For these models, we then determine the constraints coming from the measurement of the isotropic gamma-ray background by FERMI for a complete set of lepton flavor violating primary modes and over a range of DM masses from 100 GeV to 10 TeV. We fi…
The notion that dark matter and standard-model matter are connected through flavor implies a generic collider signature of the type 2 jets + $μ^\pm$ + $e^\mp$ + missing energy. We discuss the theoretical basis of this proposal and its verifiability at the Large Hadron Collider.
Lusignoli and Vignati have recently pointed out that it is in principle possible to directly detect the cosmic antineutrino background by using the rather stable isotope holmium-163 as a target, which can decay into dysprosium-163 via electron capture (EC) with a very small energy release. In this paper we calculate the rate of the relic antineutrino capture on holmium-163 nuclei against the corresponding EC decay rate by taking account of different neutrino mass hierarchies and reasonable values of theta_13. We show that such flavor effects are appreciable and even important in some cases, an…
In this paper, we propose a hexagonal description for the flavor composition of ultrahigh-energy (UHE) neutrinos and antineutrinos, which will hopefully be determined at the future large neutrino telescopes. With such a geometrical description, we are able to clearly separate the individual flavor composition of neutrinos from that of antineutrinos in one single regular hexagon, which can be regarded as a natural generalization of the widely-used ternary plot. For illustration, we consider the $pp$ or $pγ$ collisions as the dominant production mechanism for UHE neutrinos and antineutrinos in t…
We review the particle physics ingredients affecting the normalization, shape, and flavor composition of astrophysical neutrinos fluxes, such as different production modes, magnetic field effects on the secondaries (muons, pions, kaons), and flavor mixing, where we focus on p-gamma interactions. We also discuss the interplay with neutrino propagation and detection, including the possibility to detect flavor and its application in particle physics, and the use of the Glashow resonance to discriminate p-gamma from p-p interactions in the source. We illustrate the implications on fluxes and flavo…
High energy cosmic neutrino fluxes can be produced inside relativistic jets under the envelopes of collapsing stars. In the energy range E ~ (0.3 - 1e5) GeV, flavor conversion of these neutrinos is modified by various matter effects inside the star and the Earth. We present a comprehensive (both analytic and numerical) description of the flavor conversion of these neutrinos which includes: (i) oscillations inside jets, (ii) flavor-to-mass state transitions in an envelope, (iii) loss of coherence on the way to observer, and (iv) oscillations of the mass states inside the Earth. We show that con…
Reactor neutrino experiments have now observed a nonzero value for $θ_{13}$ at $5σ$, and global fits to data imply a nonzero value above $10σ$. Nonzero values for $θ_{13}$ and/or $θ_{32}-π/4$ break a $ν_μ-ν_τ$ symmetry, which has qualitative as well as quantitative implications for the time-evolution of neutrino flavors. In particular, the large-distance flavor evolution matrix, non-invertible with $ν_μ-ν_τ$ symmetry, is now invertible. This means that measurements of neutrino flavor ratios at Earth can now be inverted to directly reveal the flavor ratios injected at cosmically distant sources…
A theoretical analysis of possible influence of neutrino magnetic moments on the propagation of ultrahigh-energy cosmic neutrinos in the interstellar space is carried out under the assumption of two-neutrino mixing. The exact solution of the effective equation for neutrino evolution in the presence of a magnetic field and matter is obtained, which accounts for four neutrino species corresponding to two different flavor states with positive and negative helicities. Using most stringent astrophysical bounds on the putative neutrino magnetic moment, probabilities of neutrino flavor and spin oscil…
In an earlier work we analyzed the CP-even scalar sector of an S3 flavor model, where we identified some novel decay signatures of an exotic scalar. In this work we extend our analysis by including the complete set of scalars/pseudoscalars, revisiting the potential minimization conditions in a more general setup, setting the spectrum in conformity with the current LHC limits on the scalar mass, and identifying yet another spectacularly novel decay channel which might be revealed from an intense study of rare top decays at the LHC into modes containing multileptons of different flavors.
Measuring high energy cosmic ray electrons/positrons (CRE) provides important means for the dark matter (DM) indirect detection and for probing the nearby galactic sources. In this work, we perform a systematic analysis of the flavor structure of DM annihilations into charged leptons based on the cosmic ray CRE spectra measured by DAMPE, Fermi-LAT, AMS-02, and CALET experiments. We study the annihilations of possible TeV scale DM particles in a nearby subhalo, which is proposed to explain the possible peak-like structure of the DAMPE CRE data. We pay special attention to the possible non-reson…
We examine the feasibility of deriving neutrino mixing parameters $δ$ and $θ_{13}$ from the cosmic neutrino flavor composition under the assumption that the flavor ratios of the cosmic neutrinos at the source were $F_{ν_e}+F_{\barν_e}:F_{ν_μ}+F_{\barν_μ}: F_{ν_τ}+F_{\barν_τ}=1:2:0$. We analyze various uncertainties that enter the derivation of $δ$ and $θ_{13}$ from the ratio of the shower-like to $μ$-tracks events which is the only realistic source of information on the flavor composition at neutrino telescopes such as ICECUBE. We then examine to what extent the deviation of the initial flavor…
We examine the constraints coming from incorporating the full Standard Model gauge symmetry into the effective field theory description of flavor processes, using semileptonic decays as paradigmatic examples. Depending on the dynamics triggering electroweak symmetry breaking, different patterns of correlations between the Wilson coefficients arise. Interestingly, this implies that flavor experiments are capable of shedding light upon the nature of the Higgs boson without actually requiring Higgs final states. Furthermore, the observed correlations can simplify model-independent analyses of the…
Three topics with relation to color superconductivity in strange quark matter are discussed. 1) The r-mode instability in strange stars, which is consistent with the existence of ``ordinary'' strange quark matter stars but inconsistent with strange stars in a pure color-flavor locked state. 2) Color-flavor locked strangelets, which are more bound than normal strangelets, and have a different charge-mass relation. 3) Estimates of the strangelet flux in cosmic rays, which is relevant for strangelet detections in upcoming cosmic ray space experiments.
The ultra high energy (UHE) cosmic neutrinos are expected to play a pivotal role in the disquisition of physics beyond the standard model of particle physics as well as serve as an ideal cosmic messengers. This epitomizes the selling point of several currently running or planned neutrino telescopes. The UHE cosmic neutrinos usually perambulate gargantuan scales in the extragalactic universe having a magnetic field. If neutrinos have a finite magnetic moment ($μ_ν$) owing to quantum loop corrections, this may result in spin-flavor oscillations, which can affect the cosmic neutrino flux. Using t…
Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an order of magnitude lower than current constraints.
We discuss the B-physics signature of a supersymmetric U(2) flavor model in which the third generation scalars are relatively light (electroweak scale masses). We impose current experimental constraints on such a framework and obtain expectations for various B-physics processes. Here we present CP violation in (b->s gamma) and (b->phi K), and, Bs-Bsbar mixing. We show that if realized in nature, such a framework can be discovered in current and upcoming experiments.
Is the new state of matter formed in relativistic heavy ion collisions the deconfined quark--gluon plasma? We survey the status of several strange hadron observables and discuss how these measurement help understand the dense hadronic matter.
Observation of high energy cosmic neutrinos by ICECUBE has ushered in a new era in exploring both cosmos and new physics beyond the Standard Model (SM). In the standard picture, although mostly $ν_μ$ and $ν_e$ are produced in the source, oscillation will produce $ν_τ$ {\it en route}. Certain beyond SM scenarios, like interaction with ultralight DM can alter this picture. Thus, the flavor composition of the cosmic neutrino flux can open up the possibility of exploring certain beyond the SM scenarios that are inaccessible otherwise. We show that the $τ$ flavor holds a special place among the neu…
Over cosmic distances, astrophysical neutrino oscillations average out to a classical flavor propagation matrix $\mathscr{P}$. Thus, flavor ratios injected at the cosmic source $W_e,W_μ,W_τ$ evolve to flavor ratios at Earthly detectors $w_e,w_μ,w_τ$ according to $\vec{w}=\mathscr{P} \vec{W}$. The unitary constraint reduces the Euclidean octant to a "flavor triangle". We prove a theorem that the area of the Earthly flavor triangle is proportional to Det$(\mathscr{P})$. One more constraint would further reduce the dimensionality of the flavor triangle at Earth (two) to a line (one). We discuss f…
We consider possible leptonic three-body decays of spin-1/2, charge-asymmetric dark matter. Assuming a general Dirac structure for the four-fermion contact interactions of interest, we study the cosmic-ray electron and positron spectra and show that good fits to the current data can be obtained for both charged-lepton-flavor-conserving and flavor-violating decay channels. We find that different choices for the Dirac structure of the underlying decay operator can be significantly compensated by different choices for the dark matter mass and lifetime. The decay modes we consider provide differin…
We discuss B-meson signatures of a Supersymmetric U(2) flavor model, with relatively light (electroweak scale masses) third generation right-handed scalars. We impose current B and K meson experimental constraints on such a theory, and obtain expectations for B->X_s gamma, B->X_s glue, B->X_s l+ l-, B->phi K_s, B_s-B_sbar mixing, and the dilepton asymmetry in B_s. We show that such a theory is compatible with all current data, and furthermore, could reconcile the apparent deviations from Standard Model predictions that have been found in some experiments.
We revisit the exclusive signature $e^\pm (μ^\pm) + b\bar b$ in the associated production of the intermediate mass Higgs boson with a $W$ boson. We show that it is feasible to use this signature to identify the Higgs boson in the lower intermediate mass region ($90$ to $130$ GeV) at the LHC with reasonable acceptance cuts by assuming effective bottom-jet identification. We further demonstrate that the background can be reduced with judicious cuts down to the level of the signal.
We discuss the prospect of extracting the values of the mixing parameters $δ$ and $θ_{13}$ through the detection of cosmic neutrinos in the planned and forthcoming neutrino telescopes. We take the ratio of the muon-track to shower-like events, R, as the realistic quantity that can be measured in the neutrino telescopes. We take into account several sources of uncertainties that enter the analysis. We then examine to what extent the deviation of the initial flavor composition from w_e:w_μ:w_τ=1:2:0 can be tested.
Signatures from pion condensation and lepton flavor asymmetries in the cosmological gravitational wave background
Instituto de Física, Universidade de São Paulo（圣保罗大学物理研究所）；Instituto de Física, Universidade Federal do Rio de Janeiro（里约热内卢联邦大学物理研究所）；Institut für Theoretische Physik, J. W. Goethe Universität（歌德大学理论物理研究所）
We study the experimental signatures of top flavored dark matter (top FDM) in direct detection searches and at the LHC. We show that for a dark matter mass above 200 GeV, top FDM can be consistent with current bounds from direct detection experiments and relic abundance constraints. We also show that next generation direct detection experiments will be able to exclude the entire perturbative parameter region for top FDM. For regions of parameter space where the flavor partners of top FDM are not readily produced, the LHC signatures of top FDM are similar to those of other models previously stu…
Simple approximate expressions for the relative flavor fluxes of energetic cosmic neutrinos detected on Earth, are presented in terms of their initial fluxes at the surface of the producing cosmic sites, assuming the neutrino mixing angles to lie in the experimentally favored region. These expressions highlight the main sensitivities to the initial production fluxes as well as to small variations of the mixing angles within the experimentally preferred region, thus providing simple methods to disentangle these physical quantities from cosmic neutrino data. This is more so, due to some striking…
Inflationary scenarios motivated by high-energy physics generically contain a plethora of degrees of freedom beyond the primordial curvature perturbation. The latter interacts in a simple way with what we name "inflationary flavor eigenstates", which differ, in general, from freely propagating "mass eigenstates". We show that the mixing between these misaligned states results in new striking behaviors in the squeezed limit of the curvature perturbation three-point function, depending not only on the mass spectrum but also on the "mixing angles" of the theory. These results bring about a new pe…
We investigate collider signatures of standard model extensions featuring vector-like leptons and a flavorful scalar sector. Such a framework arises naturally within asymptotically safe model building, which tames the UV behavior of the standard model towards the Planck scale and beyond. We focus on values of Yukawa couplings and masses which allow to explain the present data on the muon and electron anomalous magnetic moments. Using a CMS search based on $77.4 \, \rm{fb}^{-1}$ at the $\sqrt{s}=13$ TeV LHC we find that flavorful vector-like leptons are excluded for masses below around $300$ Ge…
Using renormalization group methods we evaluate the thermal strangeness and charm chemical equilibrium relaxation times in the deconfined quark-gluon plasma. We present a reaction model and evaluate the total production rate of strangeness in fixed target Pb-Pb collisions at 10--300 A GeV. We discuss the relevance of our results to the diagnosis and understanding of the properties of the deconfined state.
Baryon triality (B3) is a Z3 discrete symmetry that can protect the proton from decay. Although its realization does not require supersymmetry, it is particularly appealing in the supersymmetry as an alternative to the popular R-parity. We discuss the issues in gauging B3, and present the minimal supersymmetric model with B3 as the remnant discrete symmetry of a TeV scale U(1) gauge symmetry. A flavor-dependent U(1) charge is necessary to achieve this, and it results in very distinguishable and flavorful predictions for the LHC experiments. We find a complementarity between a 2-lepton sneutrin…
We discuss neutrino fluxes and energy dependent flavor ratios of cosmic accelerators as a function of the size of the acceleration region and the magnetic field, which are the parameters of the Hillas plot. We assume that photohadronic interactions between Fermi accelerated protons and synchrotron photons from co-accelerated electrons (or positrons) lead to charged pion production. We include synchrotron cooling of the charged pions and successively produced muons, which then further decay into neutrinos, as well as the helicity dependence of the muon decays. Our photohadronic interaction mode…
Motivated by our limited knowledge of the Higgs couplings to first two generation fermions, we analyze the collider phenomenology of a class of two Higgs doublet models (2HDMs) with a non-standard Yukawa sector. One Higgs doublet is mainly responsible for the masses of the weak gauge bosons and the third generation fermions, while the second Higgs doublet provides mass for the lighter fermion generations. The characteristic collider signatures of this setup differ significantly from well-studied 2HDMs with natural flavor conservation, flavor alignment, or minimal flavor violation. New producti…
I provide a short review of the current status of indirect dark matter searches with gamma rays, charged cosmic rays and neutrinos. For each case I will focus on various excesses reported in the literature which have been interpreted as possible hints of dark matter, and I will use them as examples to discuss theoretical aspects and analysis methodologies.
The DAMPE experiment has recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the annihilation of dark matter, the DAMPE result restricts the dark matter mass and possible annihilation channels to a few case. In this paper we explain the DAMPE result with the electron-flavored $Z^\prime$-portal fermionic dark matter. We show that the Dirac dark matter scenario is promising to explain the excess via the process $\bar χχ\to\mathbf{Z}'\to \bar e e$. The reduced annihilation cross section is limited in a range of $10…
There are lots of new physics models which predict an extra neutral gauge boson, referred as Z'-boson. In a certain class of these new physics models, the Z'-boson has flavor-dependent couplings with the fermions in the Standard Model (SM). Based on a simple model in which couplings of the SM fermions in the third generation with the Z'-boson are different from those of the corresponding fermions in the first two generations, we study the signatures of Z'-boson at the Large Hadron Collider (LHC) and the International Linear Collider (ILC). We show that at the LHC, the Z'-boson with mass around…
We consider a model where the standard model is extended by the addition of a vector-like isosinglet down-type quark b'. We perform a chi square fit to the flavor physics data and obtain the preferred central values along with errors of all the elements of the measurable 3 X 4 quark mixing matrix. The fit indicates that all the new-physics parameters are consistent with zero and the mixing of the b' quark with the other three is constrained to be small. The current flavor physics data rules out possibility of detectable new physics signals in most of the flavor physics observables. We also inv…
In the early Universe above the weak scale, both baryon $B$ and lepton $L$ numbers are violated by nonperturabive effects in the Standard Model while $B-L$ remains conserved. Introducing new physics which violates perturbatively $L$ and/or $B$, one can generate dynamically a nonzero $B-L$ charge and hence a nonzero $B$ charge. In this work, we focus on the former scenario which is also known as leptogenesis. We show how to describe the evolutions of lepton flavor charges taking into account the complete Standard Model lepton flavor and spectator effects in a unified and lepton flavor basis-ind…
We consider a model with multi-charged particles including vector-like fermions and a charged scalar under a local $U(1)_{μ- τ}$ symmetry. We search for allowed parameter region explaining muon anomalous magnetic moment (muon $g-2$) and $b \to s \ell^+ \ell^-$ anomalies, satisfying constraints from the lepton flavor violations, $Z$ boson decays, meson anti-meson mixing and collider experiments. Carrying out numerical analysis, we explore the typical size of the muon $g-2$ and Wilson coefficients to explain $b \to s \ell^+ \ell^-$ anomalies in our model when all other experimental constraints a…
This is the second of two reports cataloging the principal signatures of electroweak and flavor dynamics at $\pbarp$ and $pp$ colliders. Here, we complete our overview of technicolor with a discussion of signatures specific to topcolor-assisted technicolor. We also review signatures of flavor dynamics associated with quark and lepton substructure. These occur in excess production rates for dijets and dileptons with high $E_T$ and high invariant mass. An important feature of these processes is that they exhibit fairly central angular and rapidity distributions. This report will appear in the Pr…
Cosmic strings can arise in hidden sector models with a spontaneously broken Abelian symmetry group. We have studied the couplings of the Standard Model fields to these so-called dark strings in the companion paper. Here we survey the cosmological and astrophysical observables that could be associated with the presence of dark strings in our universe with an emphasis on low-scale models, perhaps TeV. Specifically, we consider constraints from nucleosynthesis and CMB spectral distortions, and we calculate the predicted fluxes of diffuse gamma ray cascade photons and cosmic rays. For strings as …
Non-Abelian discrete symmetries have been widely used to explain the patterns of lepton masses and flavor mixing. In these models, a given symmetry is assumed at a high scale and then is spontaneously broken by scalars (the flavons), which acquire vacuum expectation values. Typically, the resulting leading order predictions for the oscillation parameters require corrections in order to comply with neutrino oscillation data. We introduce such corrections through an explicit small breaking of the symmetry. This has the advantage of solving the cosmological problems of these models without resort…
We propose a new flavor model that can simlutaneously well-describe the indirect detection experiment of (decaying) dark matter in the cosmic-ray, with the binary icosahedral group A'_5. We show not only that the A'_{5} symmetry can derive quark and lepton masses and mixings consistently, but also that are expected some predictions for the lepton sector. And if we assume a gauge-singlet fermionic decaying dark matter, its decay operators are also constrained by this symmetry so that only dimension six operators of leptonic decay are allowed up to six dimensional Lagrangians. We find that the c…
We investigate the possible formation of a Bose-Einstein condensed phase of pions in the early Universe at nonvanishing values of lepton flavor asymmetries. A hadron resonance gas model with pion interactions, based on first-principle lattice QCD simulations at nonzero isospin density, is used to evaluate cosmic trajectories at various values of electron, muon, and tau lepton asymmetries that satisfy the available constraints on the total lepton asymmetry. The cosmic trajectory can pass through the pion condensed phase if the combined electron and muon asymmetry is sufficiently large: $|l_e + …
The observation of high-energy extraterrestrial neutrinos at IceCube represents the beginning of the era of neutrino astronomy. In this paper, we study the cosmic neutrino flavor ratios against the Dirac CP-violating phase at neutrino telescopes, taking into account the charged-current and neutral-current interactions at the detectors. We then demonstrate how to probe mass hierarchy at future neutrino telescopes by the precise measurements of the cosmic neutrino flavor ratios. We show that the sensitivity of our scheme is independent of the undetermined values of the Dirac CP-violating phase. …
We consider flavor constraints on, and collider signatures of, Asymmetric Dark Matter (ADM) via higher dimension operators. In the supersymmetric models we consider, R-parity violating (RPV) operators carrying B-L interact with n dark matter (DM) particles X through an interaction of the form W = X^n O_{B-L}, where O_{B-L} = q l d^c, u^c d^c d^c, l l e^c. This interaction ensures that the lightest ordinary supersymmetric particle (LOSP) is unstable to decay into the X sector, leading to a higher multiplicity of final state particles and reduced missing energy at a collider. Flavor-violating pr…
We explore several novel LHC signatures arising from quark or lepton flavor violating couplings in the Higgs sector, and we constrain such couplings using LHC data. Since the largest signals are possible in channels involving top quarks or tau leptons, we consider in particular the following flavor violating processes: (1) $pp \to thh$ (top plus di-Higgs final state) arising from a dimension six coupling of up-type quarks to three insertions of the Higgs field. We develop a search strategy for this final state and demonstrate that detection is possible at the high luminosity LHC if flavor viol…
We study cosmic-ray anomaly observed by PAMELA based on E_6 inspired extra U(1) model with S_4 x Z_2 flavor symmetry. In our model, the lightest flavon has very long lifetime of O(10^{18)) second which is longer than the age of the universe, but not long enough to explain the PAMELA result ~ O(10^{26}) sec. Such a situation could be avoidable by considering that the flavon is not the dominant component of dark matters and the dominant one is the lightest neutralino. With appropriate parameter set, density parameter of dark matter and over-abundance of positron flux in cosmic-ray are realized a…
For high energy cosmic neutrinos Athar, Jezabek, and Yasuda (AJY) have recently shown that the existing data on neutrino oscillations suggests that cosmic neutrino flux at the AGN/GRB source, F(nu_e):F(nu_mu):F(nu_tau) approx 1:2:0, oscillates to F(nu_e):F(nu_mu):F(nu_tau) approx 1:1:1. These results can be confirmed at AMANDA, Baikal, ANTARES and NESTOR, and other neutrino detectors with a good flavor resolution. Here, we re-derive the AJY result from quasi bi-maximal mixing, and show that observation of F(nu_e):F(nu_μ):F(nu_tau) approx 1:1:1 does not necessarily establish cosmic neutrino flu…
We investigate the prospects to extract supersymmetric couplings from a decay length measurement at the LHC. Specifically, we exploit the opportunity of a light and long-lived stop which is pair-produced through gluinos in association with like-sign top quarks. Any observed finite value of the stop decay length strongly supports models in which flavor is broken in a minimal way solely by the Standard Model Yukawa couplings. We find that a 1 picosecond stop lifetime, dominated by t~ -> c chi^0 decays, yields macroscopic transverse impact parameters of about 180 microns. If the lightest neutrali…
