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D. Marfatia

Publications and source records attributed to D. Marfatia.

53 records · Page 3Linked to original sources
arXiv2003

LSND anomaly from CPT violation in four-neutrino models

The LSND signal for \barν_μto \barν_e oscillations has prompted supposition that there may be a fourth light neutrino or that CPT is violated. Neither explanation provides a good fit to all existing neutrino data. We examine the even more speculative possibility that a four-neutrino model with CPT violation can explain the LSND effect and remain consistent with all other data. We find that models with a 3+1 mass structure in the neutrino sector are viable; a 2+2 structure is permitted only in the antineutrino sector.

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arXiv2002

KamLAND and solar neutrino data eliminate the LOW solution

The KamLAND reactor antineutrino experiment has detected a 3.4σflux suppression relative to the expectation if no neutrino oscillations occur. We combine KamLAND data with solar neutrino data and show that the LMA solution is the only viable oscillation solution to the solar neutrino problem at the 4.4σC. L.

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arXiv2002

How two neutrino superbeam experiments do better than one

We examine the use of two superbeam neutrino oscillation experiments with baselines $\lsim 1000$ km to resolve parameter degeneracies inherent in the three-neutrino analysis of such experiments. We find that with appropriate choices of neutrino energies and baselines two experiments with different baselines can provide a much better determination of the neutrino mass ordering than a single experiment alone. Two baselines are especially beneficial when the mass scale for solar neutrino oscillations $δm^2_{\rm sol}$ is $\gsim 5\times10^{-5}$ eV$^2$. We also examine CP violation sensitivity and the resolution of other parameter degeneracies. We find that the combined data of superbeam experiments with baselines of 295 and 900 km can provide sensitivity to both the neutrino mass ordering and CP violation for $\sin^22θ_{13}$ down to 0.03 for $|δm^2_{\rm atm}| \simeq 3\times10^{-3}$ eV$^2$. It would be highly advantageous to have a 10% determination of $|δm^2_{\rm atm}|$ before the beam energies and baselines are finalized, although if $|δm^2_{\rm atm}|$ is not that well known, the neutrino energies and baselines can be chosen to give fairly good sensitivity for a range of $|δm^2_{\rm atm}|$.

hep-ph↗
arXiv2002

Inverting a Supernova: Neutrino Mixing, Temperatures and Binding Energy

We show that the temperatures of the emergent non-electron neutrinos and the binding energy released by a galactic Type II supernova are determinable, assuming the Large Mixing Angle (LMA) solution is correct, from observations at the Sudbury Neutrino Observatory (SNO) and at Super-Kamiokande (SK). If the neutrino mass hierarchy is inverted, either a lower or upper bound can be placed on the neutrino mixing angle $θ_{13}$, and the hierarchy can be deduced for adiabatic transitions. For the normal hierarchy, neither can $θ_{13}$ be constrained nor can the hierarchy be determined. Our conclusions are qualitatively unchanged for the proposed Hyper-Kamiokande detector.

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arXiv2002

Off--axis Beams and Detector Clusters: Resolving Neutrino Parameter Degeneracies

There are three parameter degeneracies inherent in the three--neutrino analysis of long--baseline neutrino experiments. We develop a systematic method for determining whether or not a set of measurements in neutrino oscillation appearance experiments with approximately monoenergetic beams can completely resolve these ambiguities. We then use this method to identify experimental scenarios in which the parameter degeneracies may be efficiently resolved. Generally speaking, with two appearance measurements degeneracies can occur over wide areas of the $(δ,θ_{13})$ parameter space; with three measurements they occur along lines in the parameter space and with four measurements they occur only at isolated points. If two detectors are placed at the same distance from the source but at different locations with respect to the main axis of the beam (a detector cluster), each detector will measure neutrinos at different energies. Then one run with neutrinos and one run with antineutrinos will give the four independent measurements that in principle can resolve all of the parameter degeneracies if $\sin^22θ_{13} \geq 0.002$. We also examine scenarios with detector clusters using only neutrino beams. Without detector clusters, the measurement of neutrinos and antineutrinos at a short distance and only neutrinos at a longer distance may also work.

hep-ph↗
arXiv2002

No-go for detecting CP violation via neutrinoless double beta decay

We present a necessary condition on the solar oscillation amplitude for CP violation to be detectable through neutrinoless double beta (0νββ) decay. It depends only on the fractional uncertainty in the ν_e-ν_e element of the neutrino mass matrix. We demonstrate that even under very optimistic assumptions about the sensitivity of future experiments to the absolute neutrino mass scale, and on the precision with which nuclear matrix elements that contribute to 0νββdecay are calculable, it will be impossible to detect neutrino CP violation arising from Majorana phases.

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arXiv2002

Testing radiative neutrino mass generation via R-parity violation at the Tevatron

An R-parity violating SUSY model with lepton-number violating couplings $λ'_{i33}$, i=2,3 can generate a neutrino mass spectrum that explains the recent results from neutrino oscillation experiments. These R-parity violating couplings lead to a clean signal with at least one isolated lepton and at least three tagged $b$ jets that is accessible in chargino and neutralino production at the Tevatron collider. This signature can be probed at $3 σ$ up to $m_{1/2} = 230$ GeV (320 GeV) with an integrated luminosity of $2 fb^{-1}$ ($30 fb^{-1}$).

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arXiv2002

Imprint of SNO neutral current data on the solar neutrino problem

We perform a global analysis in the framework of two active neutrino oscillations of all solar neutrino data, including the recent SNO day and night spectra (comprised of the charged current (CC), elastic scattering (ES) and neutral current (NC) events), the Super-Kamiokande (SK) day and night spectra (from 1496 days) and the updated SAGE results. We find that the Large Mixing Angle (LMA) solution is selected at the 99% C.L.; the best-fit parameters are Δm^2=5.6 \times 10^{-5} eV^2 and θ=32^{\circ}. No solutions with θ\geq π/4 are allowed at the 5σC.L. Oscillations to a pure sterile state are excluded at 5.3σ, but a sizeable sterile neutrino component could still be present in the solar flux.

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arXiv2002

Supernova 1987A did not test the neutrino mass hierarchy

We dispel the misconception that data from SN 1987A favor the normal neutrino mass hierarchy over the inverted hierarchy for $\sin^2 θ_{13} \gsim 10^{-4}$. We find comparable fits for the two hierarchies. No bound can be placed on the mixing angle $θ_{13}$ even at the 1$σ$ level.

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arXiv2002

Neutrino oscillation parameters from MINOS, ICARUS and OPERA combined

We perform a detailed analysis of the capabilities of the MINOS, ICARUS and OPERA experiments to measure neutrino oscillation parameters at the atmospheric scale with their data taken separately and in combination. MINOS will determine $Δm^2_{32}$ and $\sin^2 2θ_{23}$ to within 10% at the 99% C.L. with 10 kton-years of data. While no one experiment will determine $\sin^2 2θ_{13}$ with much precision, if its value lies in the combined sensitivity region of the three experiments, it will be possible to place a lower bound of O(0.01) at the 95% C.L. on this parameter by combining the data from the three experiments. The same bound can be placed with a combination of MINOS and ICARUS data alone.

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arXiv2001

Breaking Eight-fold Degeneracies in Neutrino CP Violation, Mixing, and Mass Hierarchy

We identify three independent two-fold parameter degeneracies (δ, θ_{13}), sgn(δm^2_{31}) and (θ_{23}, π/2-θ_{23}) inherent in the usual three-neutrino analysis of long-baseline neutrino experiments, which can lead to as much as an eight-fold degeneracy in the determination of the oscillation parameters. We discuss the implications these degeneracies have for detecting CP violation and present criteria for breaking them. A superbeam facility with a baseline at least as long as the distance between Fermilab and Homestake (1290 km) and a narrow band beam with energy tuned so that the measurements are performed at the first oscillation peak can resolve all the ambiguities other than the (θ_{23}, π/2-θ_{23}) ambiguity (which can be resolved at a neutrino factory) and a residual (δ, π-δ) ambiguity. However, whether or not CP violation occurs in the neutrino sector can be ascertained independently of the latter two ambiguities. The (δ,π-δ) ambiguity can be eliminated by performing a second measurement to which only the \cosδterms contribute. The hierarchy of mass eigenstates can be determined at other oscillation peaks only in the most optimistic conditions, making it necessary to use the first oscillation maximum. We show that the degeneracies may severely compromise the ability of the proposed SuperJHF-HyperKamiokande experiment to establish CP violation. In our calculations we use approximate analytic expressions for oscillation probabilitites that agree with numerical solutions with a realistic Earth density profile.

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arXiv2001

Unknowns after the SNO Charged-Current Measurement

We perform a model-independent analysis of solar neutrino flux rates including the recent charged-current measurement at the Sudbury Neutrino Observatory (SNO). We derive a universal sum rule involving SNO and SuperKamiokande rates, and show that the SNO neutral-current measurement can not fix the fraction of solar $ν_e$ oscillating to sterile neutrinos. The large uncertainty in the SSM $^8$B flux impedes a determination of the sterile neutrino fraction.

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arXiv2001

Neutrino Superbeam Scenarios at the Peak

We discuss options for U.S. long baseline neutrino experiments using upgraded conventional neutrino beams, assuming $L/E_ν$ is chosen to be near the peak of the leading oscillation. We find that for L = 1290 km (FNAL-Homestake) or 1770 km (FNAL-Carlsbad, or BNL-Soudan) it is possible to simultaneously have good $\sin^22θ_{13}$ reach and sgn($δm^2_{31}$) determination, and possibly sizeable $τ$ rates and some $δ$ sensitivity.

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arXiv2001

Piecing the Solar Neutrino Puzzle Together at SNO

We perform an oscillation parameter-independent analysis of solar neutrino flux measurements from which we predict the charged-current rate at SNO relative to Standard Solar Model to be $R_{SNO}^{CC}=0.35^{+0.16}_{-0.09} (0.46^{+0.13}_{-0.11})$ for oscillations to active (sterile) neutrinos. By alternately considering the $^8$B flux normalization fixed and free, we find that the flux measured by Super-Kamiokande (SK) not being a result of oscillations is strongly disfavored for oscillations to active neutrinos. SNO will determine the best-fit value of the $^8$B flux normalization $β$ (equal to the neutral-current rate), without recourse to neutral-current measurements, from the derived relation $β=R_{SNO}^{NC}=5.85 R_{SK} - 4.85 R_{SNO}^{CC}$. Using a simple parameterization of the fraction of high, intermediate, and low energy solar neutrinos starting above resonance, we reproduce the results of global analyses to good accuracy; we find that the LMA solution with a normal mass hierarchy is clearly favored. With $β$ free, our analysis for oscillations to active neutrinos gives $R_{SNO}^{NC}=β=1.34 \pm 0.34$, which corresponds to $R_{SNO}^{CC}=0.28\pm 0.07$.

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arXiv2001

Earth Regeneration of Solar Neutrinos at SNO and Super-Kamiokande

We analyze the 1258-day Super-Kamiokande day and night solar neutrino energy spectra with various $χ^2$ definitions. The best-fit lies in the LMA region at $(Δm^2, tan^2 θ)=(5.01\times 10^{-5} eV^2, 0.60)$, independently of whether systematic errors are included in the $χ^2$-definition. We compare the exclusion and allowed regions from the different definitions and choose the most suitable definition to predict the regions from SNO at the end of three years of data accumulation. We first work under the assumption that Super-Kamiokande sees a flux-suppressed flat energy spectrum. Then, we consider the possibility of each one of the three MSW regions being the solution to the solar neutrino problem. We find that the exclusion and allowed regions for the flat spectrum hypothesis and the LMA and LOW solutions are alike. In three years, we expect SNO to find very similar regions to that obtained by Super-Kamiokande. We evaluate whether the zenith angle distribution at SNO with optimum binning will add anything to the analysis of the day and night spectra; for comparison, we show the results of our analysis of the 1258-day zenith angle distribution from Super-Kamiokande, for which the best-fit parameters are $(Δm^2, tan^2 θ)=(5.01\times 10^{-5} eV^2, 0.56)$.

hep-ph↗
arXiv2000

Cosmology and Hierarchy in Stabilized Warped Brane Models

We examine the cosmology and hierarchy of scales in models with branes immersed in a five-dimensional curved spacetime subject to radion stabilization. When the radion field is time-independent and the inter-brane spacing is stabilized, the universe can naturally find itself in the radiation-dominated epoch. This feature is independent of the form of the stabilizing potential. We recover the standard Friedmann equations without assuming a specific form for the bulk energy-momentum tensor. In the models considered, if the observable brane has positive tension, a solution to the hierarchy problem requires the presence of a negative tension brane somewhere in the bulk. We find that the string scale can be as low as the electroweak scale. In the situation of self-tuning branes where the bulk cosmological constant is set to zero, the brane tensions have hierarchical values. In the case of a polynomial stabilizing potential no new hierarchy is created.

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