Measurement of Permanent Electric Dipole Moments of Charged Hadrons in Storage Rings

Permanent Electric Dipole Moments (EDMs) of elementary particles violate two fundamental symmetries: time reversal invariance (T) and parity (P). Assuming the CPT theorem this implies CP-violation. The CP-violation of the Standard Model is orders of magnitude too small to be observed experimentally in EDMs in the foreseeable future. It is also way too small to explain the asymmetry in abundance of matter and anti-matter in our universe. Hence, other mechanisms of CP violation outside the realm of the Standard Model are searched for and could result in measurable EDMs. Up to now most of the EDM measurements were done with neutral particles. With new techniques it is now possible to perform dedicated EDM experiments with charged hadrons at storage rings where polarized particles are exposed to an electric field. If an EDM exists the spin vector will experience a torque resulting in change of the original spin direction which can be determined with the help of a polarimeter. Although the principle of the measurement is simple, the smallness of the expected effect makes this a challenging experiment requiring new developments in various experimental areas. Complementary efforts to measure EDMs of proton, deuteron and light nuclei are pursued at Brookhaven National Laboratory and at Forschungszentrum Juelich with an ultimate goal to reach a sensitivity of 10^{-29} e cm.Comment: 8 pages, 2 figure

CP violation and the CKM matrix

Our knowledge of quark-flavor physics and CP violation increased tremendously over the past five years. It is confirmed that the Standard Model correctly describes the dominant parts of the observed CP-violating and flavor-changing phenomena. Not only does CP violation provide some of the most precise constraints on the flavor sector, but several measurements performed at the B-factories achieved much better precision than had been expected. We review the present status of the Cabibbo-Kobayashi-Maskawa matrix and CP violation, recollect the relevant experimental and theoretical inputs, display the results from the global CKM fit, and discuss their implications for the Standard Model and some of its extensions.Comment: 61 pages, 11 figures; review article to be published in Ann. Rev. of Nucl. and Part. Scienc

Unanswered Questions in the Electroweak Theory

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider. A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests have established so far. The outstanding unconfirmed prediction of the electroweak theory is the existence of the Higgs boson, a weakly interacting spin-zero particle that is the agent of electroweak symmetry breaking, the giver of mass to the weak gauge bosons, the quarks, and the leptons. General arguments imply that the Higgs boson or other new physics is required on the TeV energy scale. Indirect constraints from global analyses of electroweak measurements suggest that the mass of the standard-model Higgs boson is less than 200 GeV. Once its mass is assumed, the properties of the Higgs boson follow from the electroweak theory, and these inform the search for the Higgs boson. Alternative mechanisms for electroweak symmetry breaking are reviewed, and the importance of electroweak symmetry breaking is illuminated by considering a world without a specific mechanism to hide the electroweak symmetry. For all its triumphs, the electroweak theory has many shortcomings. . . .Comment: 31 pages, 20 figures; prepared for Annual Review of Nuclear and Particle Science (minor changes

CPT Violation, Strings, and Neutral-Meson Systems

This talk provides a short overview of recent results on possible CPT violation and some associated experimental signatures.Comment: Presented at Orbis Scientiae, January 199

Leptogenesis as the origin of matter

We explore in some detail the hypothesis that the generation of a primordial lepton-antilepton asymmetry (Leptogenesis) early on in the history of the Universe is the root cause for the origin of matter. After explaining the theoretical conditions for producing a matter-antimatter asymmetry in the Universe we detail how, through sphaleron processes, it is possible to transmute a lepton asymmetry -- or, more precisely, a (B-L)-asymmetry -- into a baryon asymmetry. Because Leptogenesis depends in detail on properties of the neutrino spectrum, we review briefly existing experimental information on neutrinos as well as the seesaw mechanism, which offers a theoretical understanding of why neutrinos are so light. The bulk of the review is devoted to a discussion of thermal Leptogenesis and we show that for the neutrino spectrum suggested by oscillation experiments one obtains the observed value for the baryon to photon density ratio in the Universe, independently of any initial boundary conditions. In the latter part of the review we consider how well Leptogenesis fits with particle physics models of dark matter. Although axionic dark matter and Leptogenesis can be very naturally linked, there is a potential clash between Leptogenesis and models of supersymmetric dark matter because the high temperature needed for Leptogenesis leads to an overproduction of gravitinos, which alter the standard predictions of Big Bang Nucleosynthesis. This problem can be resolved, but it constrains the supersymmetric spectrum at low energies and the nature of the lightest supersymmetric particle (LSP). Finally, as an illustration of possible other options for the origin of matter, we discuss the possibility that Leptogenesis may occur as a result of non-thermal processes.Comment: 53 pages, minor corrections, one figure and references added, matches published versio

Search for electric dipole moments at storage rings

Permanent electric dipole moments (EDMs) violate parity and time reversal symmetry. Within the Standard Model (SM) they are many orders of magnitude below present experimental sensitivity. Many extensions of the SM predict much larger EDMs, which are therefore an excellent probe for the existence of "new physics". Until recently it was believed that only electrically neutral systems could be used for sensitive searches of EDMs. With the introduction of a novel experimental method, high precision for charged systems will be within reach as well. The features of this method and its possibilities are discussed.Comment: Proc. EXA2011, 6 pages; http://www.springerlink.com/content/45l35376832vhrg0

Skyrmion Multi-Walls

Skyrmion walls are topologically-nontrivial solutions of the Skyrme system which are periodic in two spatial directions. We report numerical investigations which show that solutions representing parallel multi-walls exist. The most stable configuration is that of the square $N$-wall, which in the $N\to\infty$ limit becomes the cubically-symmetric Skyrme crystal. There is also a solution resembling parallel hexagonal walls, but this is less stable.Comment: 7 pages, 1 figur

Fermions and noncommutative emergent gravity II: Curved branes in extra dimensions

We study fermions coupled to Yang-Mills matrix models from the point of view of emergent gravity. The matrix model Dirac operator provides an appropriate coupling for fermions to the effective gravitational metric for general branes with nontrivial embedding, albeit with a non-standard spin connection. This generalizes previous results for 4-dimensional matrix models. Integrating out the fermions in a nontrivial geometrical background induces indeed the Einstein-Hilbert action of the effective metric, as well as additional terms which couple the Poisson tensor to the Riemann tensor, and a dilaton-like term.Comment: 34 pages; minor change

Leptogenesis in the presence of exact flavor symmetries

In models with flavor symmetries in the leptonic sector leptogenesis can take place in a very different way compared to the standard leptogenesis scenario. We study the generation of a $B-L$ asymmetry in these kind of models in the flavor symmetric phase pointing out that successful leptogenesis requires (i) the right-handed neutrinos to lie in different representations of the flavor group; (ii) the flavons to be lighter at least that one of the right-handed neutrino representations. When these conditions are satisfied leptogenesis proceeds due to new contributions to the CP violating asymmetry and -depending on the specific model- in several stages. We demonstrate the validity of these arguments by studying in detail the generation of the $B-L$ asymmetry in a scenario of a concrete $A_4$ flavor model realization.Comment: 25 pages, 7 figures; version 2: A few clarifications added. Version matches publication in JHE

MSSM Baryogenesis and Electric Dipole Moments: An Update on the Phenomenology

We explore the implications of electroweak baryogenesis for future searches for permanent electric dipole moments in the context of the minimal supersymmetric extension of the Standard Model (MSSM). From a cosmological standpoint, we point out that regions of parameter space that over-produce relic lightest supersymmetric particles can be salvaged only by assuming a dilution of the particle relic density that makes it compatible with the dark matter density: this dilution must occur after dark matter freeze-out, which ordinarily takes place after electroweak baryogenesis, implying the same degree of dilution for the generated baryon number density as well. We expand on previous studies on the viable MSSM regions for baryogenesis, exploring for the first time an orthogonal slice of the relevant parameter space, namely the (tan\beta, m_A) plane, and the case of non-universal relative gaugino-higgsino CP violating phases. The main result of our study is that in all cases lower limits on the size of the electric dipole moments exist, and are typically on the same order, or above, the expected sensitivity of the next generation of experimental searches, implying that MSSM electroweak baryogenesis will be soon conclusively tested.Comment: 23 pages, 10 figures, matches version published in JHE