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M. S. Berger

Publications and source records attributed to M. S. Berger.

At least 19 recordsLinked to original sources

Preoperative brain tumor imaging: models and software for segmentation and standardized reporting

For patients suffering from brain tumor, prognosis estimation and treatment decisions are made by a multidisciplinary team based on a set of preoperative MR scans. Currently, the lack of standardized and automatic methods for tumor detection and generation of clinical reports represents a major hurdle. In this study, we investigate glioblastomas, lower grade gliomas, meningiomas, and metastases, through four cohorts of up to 4000 patients. Tumor segmentation models were trained using the AGU-Net architecture with different preprocessing steps and protocols. Segmentation performances were assessed in-depth using a wide-range of voxel and patient-wise metrics covering volume, distance, and probabilistic aspects. Finally, two software solutions have been developed, enabling an easy use of the trained models and standardized generation of clinical reports: Raidionics and Raidionics-Slicer. Segmentation performances were quite homogeneous across the four different brain tumor types, with an average true positive Dice ranging between 80% and 90%, patient-wise recall between 88% and 98%, and patient-wise precision around 95%. With our Raidionics software, running on a desktop computer with CPU support, tumor segmentation can be performed in 16 to 54 seconds depending on the dimensions of the MRI volume. For the generation of a standardized clinical report, including the tumor segmentation and features computation, 5 to 15 minutes are necessary. All trained models have been made open-access together with the source code for both software solutions and validation metrics computation. In the future, an automatic classification of the brain tumor type would be necessary to replace manual user input. Finally, the inclusion of post-operative segmentation in both software solutions will be key for generating complete post-operative standardized clinical reports.

eess.IV

Lorentz and CPT Violation in Heavy Quark Physics

Violations of the Lorentz and CPT symmetries can appear as observable effects in the direct production of top quarks and their subsequent decays. Earlier results for the $q\bar{q}$ production process for $t\bar{t}$ pairs have been extended to include the gluon fusion process which dominates at the LHC. In addition results are obtained for testing CPT symmetry through single top quark production.

hep-ph

Lorentz Violation in Top-Quark Physics

Lorentz and CPT violation can affect the rates for $t$-$\ol t$ production and decay. The Lorentz-violating coefficients in the Standard-Model Extension responsible for modifying the top-quark events have recently been bounded by the D0 Collaboration. To extend the analysis to the LHC the calculations need to be extended to include the gluon fusion production mechanism. Some of the first results of this program were presented at the Meeting.

hep-ph

Spacetime Symmetry Violation

Supersymmetric models with Lorentz violation can be formulated in superspace. Two theories based on the Wess-Zumino model are discussed. A compactification of superspace can be employed to understand the chiral superfield that arises in the models.

hep-ph

Lorentz Violation in Supersymmetric Field Theories

Broken spacetime symmetries might emerge from a fundamental physical theory. The effective low-energy theory might be expected to exhibit violations of supersymmetry and Lorentz invariance. Some illustrative models which combine supersymmetry and Lorentz violation are described, and a superspace formulation is given.

hep-ph

Superfield Realizations of Lorentz Violation

Lorentz-violating extensions of the Wess-Zumino model have been formulated in superspace. The models respect a supersymmetry algebra and can be understood as arising from suitably modified superspace transformations.

hep-ph

Superfield Realizations of Lorentz and CPT Violation

Superfield realizations of Lorentz-violating extensions of the Wess-Zumino model are presented. These models retain supersymmetry but include terms that explicitly break the Lorentz symmetry. The models can be understood as arising from superspace transformations that are modifications of the familiar one in the Lorentz-symmetric case.

hep-th

Lorentz Violation and Spacetime Supersymmetry

Supersymmetry and Lorentz invariance are closely related as both are spacetime symmetries. Terms can be added to Lagrangians that explicitly break either supersymmetry or Lorentz invariance. It is possible to include terms which violate Lorentz invariance but maintain invariance under supersymmetric transformations. I illustrate this with some simple extensions of the original Wess-Zumino model.

hep-ph

Leptogenesis and Low-energy Observables

We relate leptogenesis in a class of theories to low-energy experimental observables: quark and lepton masses and mixings. With reasonable assumptions motivated by grand unification, one can show that the CP-asymmetry parameter takes a universal form. Furthermore the dilution mass is related to the light neutrino masses. Overall, these models offer a natural explanation for a lepton asymmetry in the early universe.

hep-ph

Supersymmetry and Lorentz Violation

Supersymmetric field theories can be constructed that violate Lorentz and CPT symmetry. We illustrate this with some simple examples related to the original Wess-Zumino model.

hep-th

Higgs Bosons at Muon Colliders

We review the role of a muon collider in the study of Higgs bosons via production in the s-channel. Very precise measurements of a Standard Model-like Higgs boson mass and total width can be performed, and may lead to a discrimination between a Standard Model Higgs boson and the light Higgs boson of the minimal supersymmetric theory. The heavier Higgs bosons from a supersymmetric theory or an exotic Higgs sector can be studied in the s-channel. A muon collider may play a crucial role in separating the overlapping signals for two heavy nearly degenerate Higgs bosons, and may play an important role in precision tests of radiative corrections in the Higgs sector. The measurements at a muon collider will be complementary to the Higgs studies at the Large Hadron Collider and at an electron-positron Linear Collider.

hep-ph

Higgs Sector Radiative Corrections and s-Channel Production

Higgs boson mass sum rules of supersymmetric models offer attractive targets for precision tests at future muon colliders. These sum rules involve the gauge boson masses as well as the masses of the Higgs boson states which can be precisely measured in the $s$-channel production process at a muon collider. These measurements can sensitively probe radiative corrections to the Higgs boson masses as well as test for CP-violation and nonminimality of the Higgs sector.

hep-ph

Discrete Flavor Symmetries and Mass Matrix Textures

We show how introducing discrete Abelian flavor symmetries can produce texture zeros in the fermion mass matrices, while preserving the correct relationships with the low-energy data on quark and lepton masses. We outline a procedure for defining texture zeros as suppressed entries in Yukawa matrices. These texture zeros can account for the coexistence of the observed large mixing in atmospheric neutrino oscillations with a hierarchy in the neutrino masses, and offer the possibility of alignment of the quark and squark mass matrices, and thus giving a solution to the supersymmetric flavor problem. A requirement that the flavor symmetry commutes with the SU(5) grand unified group can be used to explain the lepton mass hierarchies as well as the neutrino parameters, including the large mixing observed in the atmospheric neutrino data. We present one such model that yields a large atmospheric neutrino mixing angle, as well as a solar neutrino mixing angle of order $λ\simeq 0.22$.

hep-ph

Anomaly-Free Flavor Symmetry and Neutrino Anarchy

We show that one can describe the quark and lepton masses with a single anomaly-free U(1) flavor symmetry provided a single order one parameter is enhanced by roughly 4-5. The flavor symmetry can be seen to arise from inside the $E_6$ symmetry group in such a way that it commutes with the SU(5) grand unified gauge group. The scenario does not distinguish between the left-handed lepton doublets and hence is a model of neutrino anarchy. It can therefore account for the large mixing observed in atmospheric neutrino experiments and predicts that the solar neutrino oscillation data is consistent with the large mixing angle solution of matter-enhanced oscillations.

hep-ph

Abelian family symmetries and Leptogenesis

We study the impact of a set of horizontal symmetries on the requirements for producing the baryon asymmetry of the universe via leptogenesis. We find that Abelian horizontal symmetries lead to a simple description of the parameters describing leptogenesis in terms of the small expansion parameter that arises from spontaneous symmetry breaking. If the family symmetry is made discrete, then an enhancement in the amount of leptogenesis can result.

hep-ph

SUSY Thresholds at a Muon Collider

One of the useful features of muon colliders is the naturally narrow spread in beam energies. Measurements of threshold cross sections then become a prime candidate for precision measurements of particle masses, widths, and couplings as well as determining particle spin. We describe the potential for measuring cross sections near threshold in supersymmetric theories.

hep-ph

Muon Collider Physics at Very High Energies

Muon colliders might greatly extend the energy frontier of collider physics. One can contemplate circular colliders with center-of-mass energies in excess of 10 TeV. Some physics issues that might be relevant at such a machine are discussed.

hep-ph

Production of Z Boson Pairs via Gluon Fusion in the Minimal Supersymmetric Model

We present the full one-loop calculation for $gg \to ZZ$ in the Minimal Supersymmetric Model (MSSM) including nonresonant contributions from the squark loop diagrams and provide analytical expressions for the helicity amplitudes. The one-loop process $gg \to ZZ$ via quark loops has been calculated in the Standard Model. In supersymmetric models, additional contributions arise from squark loops. In some regions of the MSSM parameter space, the top and bottom squark loops can make important contributions to the diagrams involving Higgs bosons. The heavy Higgs scalar (H) might be detected at the Large Hadron Collider via $gg \to H \to ZZ$ for $\tanβ\alt 5$.

hep-ph