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B. Kayser

Publications and source records attributed to B. Kayser.

17 recordsLinked to original sources
arXiv2015

The Intermediate Neutrino Program

The US neutrino community gathered at the Workshop on the Intermediate Neutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 to explore opportunities in neutrino physics over the next five to ten years. Scientists from particle, astroparticle and nuclear physics participated in the workshop. The workshop examined promising opportunities for neutrino physics in the intermediate term, including possible new small to mid-scale experiments, US contributions to large experiments, upgrades to existing experiments, R&D plans and theory. The workshop was organized into two sets of parallel working group sessions, divided by physics topics and technology. Physics working groups covered topics on Sterile Neutrinos, Neutrino Mixing, Neutrino Interactions, Neutrino Properties and Astrophysical Neutrinos. Technology sessions were organized into Theory, Short-Baseline Accelerator Neutrinos, Reactor Neutrinos, Detector R&D and Source, Cyclotron and Meson Decay at Rest sessions.This report summarizes discussion and conclusions from the workshop.

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arXiv2013

Neutrinos

This document represents the response of the Intensity Frontier Neutrino Working Group to the Snowmass charge. We summarize the current status of neutrino physics and identify many exciting future opportunities for studying the properties of neutrinos and for addressing important physics and astrophysics questions with neutrinos.

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arXiv2008

DUSEL Theory White Paper

The NSF has chosen the site for the Deep Underground Science and Engineering Laboratory (DUSEL) to be in Lead, South Dakota. In fact, the state of South Dakota has already stepped up to the plate and contributed its own funding for the proposed lab, see http://www.sanfordlaboratoryathomestake.org/index.html. The final decision by NSF for funding the Initial Suite of Experiments for DUSEL will be made early in 2009. At that time the NSF Science Board must make a decision. Of order 200 experimentalists have already expressed an interest in performing experiments at DUSEL. In order to assess the interest of the theoretical community, the Center for Cosmology and Astro-Particle Physics (CCAPP) at The Ohio State University (OSU) organized a 3-day DUSEL Theory Workshop in Columbus, Ohio from April 4 - 6, 2008. The workshop focused on the scientific case for six proposed experiments for DUSEL: long baseline neutrino oscillations, proton decay, dark matter, astrophysical neutrinos, neutrinoless double beta decay and N-Nbar oscillations. The outcome of this workshop is the DUSEL Theory White paper addressing the scientific case at a level which may be useful in the decision making process for policy makers at the NSF and in the U.S. Congress. In order to assess the physics interest in the DUSEL project we have posted the DUSEL Theory White paper on the following CCAPP link http://ccapp.osu.edu/whitepaper.html . Please read the white paper and, if you are interested, use the link to show your support by co-signing the white paper.

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arXiv2005

Theory of Neutrinos: A White Paper

During 2004, four divisions of the American Physical Society commissioned a study of neutrino physics to take stock of where the field is at the moment and where it is going in the near and far future. Several working groups looked at various aspects of this vast field. The summary was published as a main report entitled ``The Neutrino Matrix'' accompanied by short 50 page versions of the report of each working group. Theoretical research in this field has been quite extensive and touches many areas and the short 50 page report provided only a brief summary and overview of few of the important points. The theory discussion group felt that it may be of value to the community to publish the entire study as a white paper and the result is the current article. After a brief overview of the present knowledge of neutrino masses and mixing and some popular ways to probe the new physics implied by recent data, the white paper summarizes what can be learned about physics beyond the Standard Model from the various proposed neutrino experiments. It also comments on the impact of the experiments on our understanding of the origin of the matter-antimatter asymmetry of the Universe and the basic nature of neutrino interactions as well as the existence of possible additional neutrinos. Extensive references to original literature are provided.

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arXiv2002

CPT Violation and the Nature of Neutrinos

In order to accommodate the neutrino oscillation signals from the solar, atmospheric, and LSND data, a sterile fourth neutrino is generally invoked, though the fits to the data are becoming more and more constrained. However, it has recently been shown that the data can be explained with only three neutrinos, if one invokes CPT violation to allow different masses and mixing angles for neutrinos and antineutrinos. We explore the nature of neutrinos in such CPT-violating scenarios. Majorana neutrino masses are allowed, but in general, there are no longer Majorana neutrinos in the conventional sense. However, CPT-violating models still have interesting consequences for neutrinoless double beta decay. Compared to the usual case, while the larger mass scale (from LSND) may appear, a greater degree of suppression can also occur.

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arXiv2001

The Potential for Neutrino Physics at Muon Colliders and Dedicated High Current Muon Storage Rings

Conceptual design studies are underway for muon colliders and other high-current muon storage rings that have the potential to become the first true ``neutrino factories''. Muon decays in long straight sections of the storage rings would produce precisely characterized beams of electron and muon type neutrinos of unprecedented intensity. This article reviews the prospects for these facilities to greatly extend our capabilities for neutrino experiments, largely emphasizing the physics of neutrino interactions.

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arXiv2000

Physics at a Neutrino Factory

In response to the growing interest in building a Neutrino Factory to produce high intensity beams of electron- and muon-neutrinos and antineutrinos, in October 1999 the Fermilab Directorate initiated two six-month studies. The first study, organized by N. Holtkamp and D. Finley, was to investigate the technical feasibility of an intense neutrino source based on a muon storage ring. This design study has produced a report in which the basic conclusion is that a Neutrino Factory is technically feasible, although it requires an aggressive R&D program. The second study, which is the subject of this report, was to explore the physics potential of a Neutrino Factory as a function of the muon beam energy and intensity, and for oscillation physics, the potential as a function of baseline.

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arXiv2000

Fate of the Sterile Neutrino

In light of recent Super-Kamiokande data and global fits that seem to exclude both pure ν_μ\to ν_s oscillations of atmospheric neutrinos and pure ν_e \to ν_s oscillations of solar neutrinos (where ν_s is a sterile neutrino), we reconsider four-neutrino models to explain the LSND, atmospheric, and solar neutrino oscillation indications. We argue that the solar data, with the exception of the ^{37}Cl results, are suggestive of ν_e \to ν_s oscillations that average to a probability of approximately 1/2. In this interpretation, with two pairs of nearly degenerate mass eigenstates separated by order 1 eV, the day-night asymmetry, seasonal dependence, and energy dependence for ^8B neutrinos should be small. Alternatively, we find that four-neutrino models with one mass eigenstate widely separated from the others (and with small sterile mixings to active neutrinos) may now be acceptable in light of recently updated LSND results; the ^{37}Cl data can be accommodated in this model. For each scenario, we present simple four-neutrino mixing matrices that fit the stated criterion and discuss future tests.

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arXiv2000

B-Decay CP Asymmetries, Discrete Ambiguities and New Physics

The first measurements of CP violation in the $B$ system will likely probe $\sin 2α$, $\sin 2β$ and $\cos 2γ$. Assuming that the CP angles $α$, $β$ and $γ$ are the interior angles of the unitarity triangle, these measurements determine the angle set $(α,β,γ)$ except for a twofold discrete ambiguity. If one allows for the possibility of new physics, the presence of this discrete ambiguity can make its discovery difficult: if only one of the two candidate solutions is consistent with constraints from other measurements in the $B$ and $K$ systems, one is not sure whether new physics is present or not. We review the methods used to resolve the discrete ambiguity and show that, even in the presence of new physics, they can usually be used to uncover this new physics. There are some exceptions, which we describe in detail. We systematically scan the parameter space and present examples of values of $(α,β,γ)$ and the new-physics parameters which correspond to all possibilities. Finally, we show that if one relaxes the assumption that the bag parameters $\BBd$ and $\BK$ are positive, one can no longer definitively establish the presence of new physics.

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arXiv1999

Exploring CP Violation with B_d -> D K_s Decays

We (re)examine CP violation in the decays B_d -> D K_s, where D represents D^0, D(bar), or one of their excited states. The quantity $\sin^2(2β+ γ)$ can be extracted from the time-dependent rates for $B_d(t) -> {\bar D}^{**0} K_s$ and $B_d(t) -> D^{**0} K_s$, where the $D^{**0}$ decays to $D^{(*)+}π^-$. If one considers a non-CP-eigenstate hadronic final state to which both D(bar) and D^0 can decay (e.g. $K^+π^-$), then one can obtain two of the angles of the unitarity triangle from measurements of the time-dependent rates for $B_d(t) -> (K^+π^-)_{D K_s}$ and $B_d(t) -> (K^-π^+)_{D K_s}$. There are no penguin contributions to these decays, so all measurements are theoretically clean.

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arXiv1999

Constraints from Neutrino Oscillation Experiments on the Effective Majorana Mass in Neutrinoless Double $β$-Decay

We determine the possible values of the effective Majorana neutrino mass $|< m > |= |\sum_j U_{ej}^2 m_j|$ in the different phenomenologically viable three and four-neutrino scenarios. The quantities $U_{αj}$ ($α= e,μ,τ,...$) denote the elements of the neutrino mixing matrix and the Majorana neutrino masses $m_j$ ($j=1,2,3,...$) are ordered as $m_1 < m_2 < ... $ Assuming $m_1 \ll m_3$ in the three-neutrino case and $m_1 \ll m_4$ in the four-neutrino case, we discuss, in particular, how constraints on $| < m > |$ depend on the mixing angle relevant in solar neutrino oscillations and on the three mass-squared differences obtained from the analyses of the solar, atmospheric and LSND data. If neutrinoless double $β$-decay proceeds via the mechanism involving $|< m >|$, conclusions about neutrinoless double $β$-decay can be drawn. If one of the two viable four-neutrino schemes (Scheme A) is realized in nature, $|< m >|$ can be as large as 1 eV and neutrinoless double $β$-decay could possibly be discovered in the near future. In this case a Majorana CP phase of the mixing matrix $U$ could be determined. In the other four-neutrino scheme (Scheme B) there is an upper bound on $|< m >|$ of the order of $10^{-2}$ eV. In the case of three-neutrino mixing the same is true if the neutrino mass spectrum is hierarchical, however, if there exist two quasi-degenerate neutrinos and the first neutrino has a much smaller mass, values of $|< m >|$ as large as $\sim 0.1$ eV are possible.

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arXiv1998

Quark Mixing and CP Violation

We review the historical developments leading to the Cabibbo-Kobayashi-Maskawa (CKM) quark mixing matrix. Present status of the CKM matrix from direct measurements is summarized, giving also the present profile of the unitarity triangle. CP Violation in the $K^0$ - $\bar{K^0}$ complex and in $B$-meson decays are discussed in the context of the CKM matrix.

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arXiv1996

Report of the Supersymmetry Theory Working Group

We provide a mini-guide to some of the possible manifestations of weak scale supersymmetry. For each of six scenarios we provide a brief description of the theoretical underpinnings, the adjustable parameters, a qualitative description of the associated phenomenology at future colliders, comments on how to simulate each scenario with existing event generators.

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arXiv1996

Cascade Mixing, a New Kind of Particle Mixing Phenomenon

We discuss ``cascade mixing", where one particle mixture, say a B0, leads to another, say a K0. A simple analysis is possible in the amplitude approach, which avoids ``collapses of the wavefunction" and is explicitly covariant. Some novel possibilities, both of conceptual and perhaps of experimental interest, arise. For example, we explain how such processes can allow one to ``tune", in principle, the phase relations in a particle mixture. Also, effects arise involving combinations of the mass differences of two particle mixtures. We explain how an intermediate measurement may play the role of a regenerator, so that in principle regeneration-like effects can be induced for the B0 and D0 systems, despite their short flight paths. The analysis of such process with respect to CP and the distinction between ``direct" and ``indirect" CP violation is discussed.

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arXiv1994

Outcome from Spontaneous CP Violation for B Decays

In the aspon model solution of the strong $CP$ problem, there is a gauged $U(1)$ symmetry, spontaneously broken by the same vacuum expectation value which breaks $CP$, whose massive gauge boson provides an additional mechanism of weak $CP$ violation. We calculate the $CP$ asymmetries in $B$ decays for the aspon model and show that they are typically smaller than those predicted from the standard model. A linear relation between the $CP$ asymmetries of different decay processes is obtained.

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arXiv1993

In Pursuit of Gamma

After reviewing techniques for extracting clean information on CP-violating phase angles from $B$ decays, we explain the rules for finding decay modes that can probe the phase angle $γ$ of the unitarity triangle. We identify the more promising of these ``$γ$ modes,'' estimate their branching ratios, and examine the degree to which they are theoretically clean. We then show that when the quark mixing matrix is not approximated as usual, but is treated exactly, none of the ``$γ$ modes'' actually measures $γ$. Rather, each of them measures $γ$ plus some correction. In all modes, the correction is small enough to be disregarded in first-generation experiments, but in some of them, it may be large enough to be observed in second-generation experiments. Our treatment of the $γ$ modes calls attention to the fact that when the quark mixing matrix is treated exactly, there are six unitarity triangles, rather than just one triangle. However, only four of the angles in these six triangles are independent. Examining the role played by these four angles, we discover that, in principle at least, measurements of nothing but CP-violating asymmetries in $B$ decays are sufficient to determine the entire quark mixing matrix.

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