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Full-Text Articles in Physics

Electron And Hole Drift Mobility Measurements On Thin Film Cdte Solar Cells, Qi Long, Steluta A. Dinca, Eric A. Schiff, Ming Yu, Jeremy Theil Jul 2014

Electron And Hole Drift Mobility Measurements On Thin Film Cdte Solar Cells, Qi Long, Steluta A. Dinca, Eric A. Schiff, Ming Yu, Jeremy Theil

Physics

We report electron and hole drift mobilities in thin film polycrystalline CdTe solar cells based on photocarrier time-of-flight measurements. For a deposition process similar to that used for high-efficiency cells, the electron drift mobilities are in the range of 10–100 cm2/Vs, and holes are in the range of 1–10 cm2/Vs. The electron drift mobilities are about a thousand times smaller than those measured in single crystal CdTe with time-of-flight; the hole mobilities are about ten times smaller. Cells were examined before and after a vapor phase treatment with CdCl2; treatment had little effect ...


Electron Drift-Mobility Measurements In Polycrystalline Cuin1-Xgaxse2 Solar Cells, Steluta A. Dinca, Eric A. Schiff, William N. Shafarman, Brian Egaas, Rommel Noufi, David L. Young Mar 2012

Electron Drift-Mobility Measurements In Polycrystalline Cuin1-Xgaxse2 Solar Cells, Steluta A. Dinca, Eric A. Schiff, William N. Shafarman, Brian Egaas, Rommel Noufi, David L. Young

Physics

We report photocarrier time-of-flight measurements of electron drift mobilities for the p-type CuIn1-xGaxSe2 films incorporated in solar cells. The electron mobilities range from 0.02 to 0.05 cm^2/Vs and are weakly temperature-dependent from 100–300 K. These values are lower than the range of electron Hall mobilities (2-1100 cm2/Vs) reported for n-type polycrystalline thin films and single crystals. We propose that the electron drift mobilities are properties of disorder-induced mobility edges and discuss how this disorder could increase cell efficiencies.


Are Three Flavors Special?, Joseph Schechter, Amir H. Fariborz, Renata Jora, M. Naeem Shahid Dec 2011

Are Three Flavors Special?, Joseph Schechter, Amir H. Fariborz, Renata Jora, M. Naeem Shahid

Physics

It has become clearer recently that the regular pattern of three flavor nonets describing the low spin meson multiplets seems to require some modification for the case of the spin 0 scalar mesons. One picture which has had some success, treats the scalars in a chiral Lagrangian framework and considers them to populate two nonets. These are, in turn, taken to result from the mixing of two "bare" nonets, one of which is of quark- antiquark type and the other of two quark- two antiquark type. Here we show that such a mixing is, before chiral symmetry breaking terms are ...


De Sitter Gravity From Lattice Gauge Theory, Simon Catterall, Daniel Ferrante, Arwen Nicholson Nov 2011

De Sitter Gravity From Lattice Gauge Theory, Simon Catterall, Daniel Ferrante, Arwen Nicholson

Physics

We investigate a lattice model for Euclidean quantum gravity based on discretization of the Palatini formulation of General Relativity. Using Monte Carlo simulation we show that while a naive approach fails to lead to a vacuum state consistent with the emergence of classical spacetime, this problem may be evaded if the lattice action is supplemented by an appropriate counter term. In this new model we find regions of the parameter space which admit a ground state which can be interpreted as (Euclidean) de Sitter space.


Thermodynamic Limit To Photonic-Plasmonic Light-Trapping In Thin Films On Metals, Eric A. Schiff Nov 2011

Thermodynamic Limit To Photonic-Plasmonic Light-Trapping In Thin Films On Metals, Eric A. Schiff

Physics

We calculate the maximum optical absorptance enhancements in thin semiconductor films on metals due to structures that diffuse light and couple it to surface plasmon polaritons. The calculations can be used to estimate plasmonic effects on light-trapping in solar cells. The calculations are based on the statistical distribution of energy in the electromagnetic modes of the structure, which include surface plasmon polariton modes at the metal interface as well as the trapped waveguide modes in the film. The enhancement has the form 4n2+/h (n – film refractive index, λ – optical wavelength, h – film thickness), which is an ...


A Measurement Of The Semileptonic Branching Fraction Of The B_S Meson, Duncan Brown, J. P. Lees Oct 2011

A Measurement Of The Semileptonic Branching Fraction Of The B_S Meson, Duncan Brown, J. P. Lees

Physics

We report a measurement of the inclusive semileptonic branching fraction of the B_s meson using data collected with the BaBar detector in the center-of-mass (CM) energy region above the Upsilon(4S) resonance. We use the inclusive yield of phi mesons and the phi yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B_s mesons relative to all B mesons as a function of CM energy. The inclusive semileptonic branching fraction of the B_s meson is determined to be B(B_s to l nu X)=9.5 (+2 ...


The Importance Of Slow-Roll Corrections During Multi-Field Inflation, Scott Watson, Anastasios Avgoustidis, Sera Cremonini, Anne-Christine Davis Oct 2011

The Importance Of Slow-Roll Corrections During Multi-Field Inflation, Scott Watson, Anastasios Avgoustidis, Sera Cremonini, Anne-Christine Davis

Physics

We re-examine the importance of slow-roll corrections during the evolution of cosmological perturbations in models of multi-field inflation. We find that in many instances the presence of light degrees of freedom leads to situations in which next to leading order slow-roll corrections become significant. Examples where we expect such corrections to be crucial include models in which modes exit the Hubble radius while the inflationary trajectory undergoes an abrupt turn in field space, or during a phase transition. We illustrate this with two examples -- hybrid inflation and double quadratic inflation. Utilizing both analytic estimates and full numerical results, we find ...


Generic Phases Of Cross-Linked Active Gels: Relaxation, Oscillation And Contractility, Shiladitya Banerjee, Tanniemola B. Liverpool, M. C. Marchetti Oct 2011

Generic Phases Of Cross-Linked Active Gels: Relaxation, Oscillation And Contractility, Shiladitya Banerjee, Tanniemola B. Liverpool, M. C. Marchetti

Physics

We study analytically and numerically a generic continuum model of an isotropic active solid with internal stresses generated by non-equilibrium `active' mechano-chemical reactions. Our analysis shows that the gel can be tuned through three classes of dynamical states by increasing motor activity: a constant unstrained state of homogeneous density, a state where the local density exhibits sustained oscillations, and a steady-state which is spontaneously contracted, with a uniform mean density.


Systematic Errors Of The Mcrg Method, Simon Catterall, Luigi Del Debbio, Joel Giedt, Liam Keegan Oct 2011

Systematic Errors Of The Mcrg Method, Simon Catterall, Luigi Del Debbio, Joel Giedt, Liam Keegan

Physics

We present a Monte Carlo Renormalisation Group (MCRG) study of the SU(2) gauge theory with two Dirac fermions in the adjoint representation. Using the two-lattice matching technique we measure the running of the coupling and the anomalous mass dimension. We find slow running of the coupling, compatible with an infrared fixed point. Assuming this running is negligible we find a vanishing anomalous dimension, gamma=-0.03(13), however without this assumption our uncertainty in the running of the coupling leads to a much larger range of allowed values, -0.6 < gamma < 0.6. We discuss the systematic errors affecting the current analysis and possible improvements.


Search For Lepton-Number Violating Processes In B+ -> H- L+ L+ Decays, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia Oct 2011

Search For Lepton-Number Violating Processes In B+ -> H- L+ L+ Decays, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia

Physics

A search is performed for the lepton number violating decay B^{+}\rightarrow h^- \mu^+ \mu^+, where h^- represents a K^- or a \pi^-, using data from the LHCb detector corresponding to an integrated luminosity of 36pb^{-1}. The decay is forbidden in the Standard Model but allowed in models with a Majorana neutrino. No signal is observed in either channel and limits of B(B^{+} \rightarrow K^- \mu^+ \mu^+) < 5.4\times 10^{-8} and B(B^{+} \rightarrow \pi^- \mu^+ \mu^+) < 5.8\times 10^{-8} are set at the 95% confidence level. These improve the previous best limits by factors of 40 and 30, respectively.


Three-Dimensional Folding Of The Triangular Lattice, Mark Bowick, P Di Francesco, Oliver Golinelli, Emmanuel Guitter Oct 2011

Three-Dimensional Folding Of The Triangular Lattice, Mark Bowick, P Di Francesco, Oliver Golinelli, Emmanuel Guitter

Physics

We study the folding of the regular triangular lattice in three dimensional embedding space, a model for the crumpling of polymerised membranes. We consider a discrete model, where folds are either planar or form the angles of a regular octahedron. These "octahedral" folding rules correspond simply to a discretisation of the 3d embedding space as a Face Centred Cubic lattice. The model is shown to be equivalent to a 96--vertex model on the triangular lattice. The folding entropy per triangle ${\rm ln} q_{3d}$ is evaluated numerically to be $q_{3d}=1.43(1)$. Various exact bounds on $q_{3d ...


Search For The Lepton Number Violating Decays B+ → Π- Μ+Μ+ And B+→ K-Μ+ Μ+, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia Oct 2011

Search For The Lepton Number Violating Decays B+ → Π- Μ+Μ+ And B+→ K-Μ+ Μ+, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia

Physics

A search is performed for the lepton number violating decay B^{+}\rightarrow h^- \mu^+ \mu^+, where h^- represents a K^- or a \pi^-, using data from the LHCb detector corresponding to an integrated luminosity of 36pb^{-1}. The decay is forbidden in the Standard Model but allowed in models with a Majorana neutrino. No signal is observed in either channel and limits of B(B^{+} \rightarrow K^- \mu^+ \mu^+) < 5.4\times 10^{-8} and B(B^{+} \rightarrow \pi^- \mu^+ \mu^+) < 5.8\times 10^{-8} are set at the 95% confidence level. These improve the previous best limits by factors of 40 and 30, respectively.


All-Sky Search For Periodic Gravitational Waves In The Full S5 Ligo Data, Duncan Brown, J. Abadie, Stefan Ballmer, Collin Capano, P. Couvares Oct 2011

All-Sky Search For Periodic Gravitational Waves In The Full S5 Ligo Data, Duncan Brown, J. Abadie, Stefan Ballmer, Collin Capano, P. Couvares

Physics

We report on an all-sky search for periodic gravitational waves in the frequency band 50-800 Hz and with the frequency time derivative in the range of 0 through -6e-9 Hz/s. Such a signal could be produced by a nearby spinning and slightly non-axisymmetric isolated neutron star in our galaxy. After recent improvements in the search program that yielded a 10x increase in computational efficiency, we have searched in two years of data collected during LIGO's fifth science run and have obtained the most sensitive all-sky upper limits on gravitational wave strain to date. Near 150 Hz our upper ...


Measurements Of The Branching Fractions For B_(S) -> D_(S)Πππ And Λ_B^0 -> Λ_C^+Πππ, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia Sep 2011

Measurements Of The Branching Fractions For B_(S) -> D_(S)Πππ And Λ_B^0 -> Λ_C^+Πππ, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia

Physics

Branching fractions of the decays H_b\to H_c\pi^-\pi^+\pi^- relative to H_b\to H_c\pi^- are presented, where H_b (H_c) represents B^0-bar(D^+), B^- (D^0), B_s^0-bar (D_s^+) and \Lambda_b^0 (\Lambda_c^+). The measurements are performed with the LHCb detector using 35{\rm pb^{-1}} of data collected at \sqrt{s}=7 TeV. The ratios of branching fractions are measured to be B(B^0-bar -> D^+\pi^-\pi^+\pi^-)/ B(B^0-bar -> D^+\pi^-) = 2.38\pm0.11\pm0.21 B(B^- -> D^0\pi^-\pi^+\pi^-) / B(B^- -> D^0\pi^-) = 1.27\pm0.06 ...


Measurements Of The Branching Fractions For B(S) → D(S)Πππ And Λb0 → Λc+Πππ, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia Sep 2011

Measurements Of The Branching Fractions For B(S) → D(S)Πππ And Λb0 → Λc+Πππ, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia

Physics

Branching fractions of the decays H_b\to H_c\pi^-\pi^+\pi^- relative to H_b\to H_c\pi^- are presented, where H_b (H_c) represents B^0-bar(D^+), B^- (D^0), B_s^0-bar (D_s^+) and \Lambda_b^0 (\Lambda_c^+). The measurements are performed with the LHCb detector using 35{\rm pb^{-1}} of data collected at \sqrt{s}=7 TeV. The ratios of branching fractions are measured to be B(B^0-bar -> D^+\pi^-\pi^+\pi^-)/ B(B^0-bar -> D^+\pi^-) = 2.38\pm0.11\pm0.21 B(B^- -> D^0\pi^-\pi^+\pi^-) / B(B^- -> D^0\pi^-) = 1.27\pm0.06 ...


Amplitude Analyses Of The Decays Χc1 →Ηπ+Π- And Χc1→Η'Π+Π-, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Sep 2011

Amplitude Analyses Of The Decays Χc1 →Ηπ+Π- And Χc1→Η'Π+Π-, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using a data sample of 2.59 x 10^7 psi(2S) decays obtained with the CLEO-c detector, we perform amplitude analyses of the complementary decay chains chi_c1 -> eta pi+ pi- and chi_c1 -> eta' pi+ pi-. We find evidence for a P-wave eta' pi scattering amplitude, which, if interpreted as a resonance, would have exotic J^PC = 1^-+ and parameters consistent with the pi_1(1600) state reported in other production mechanisms. We also make the first observation of the decay a_0(980) -> eta' pi and measure the ratio of branching fractions B(a_0(980) -> eta' pi)/B(a_0(980) -> eta ...


Amplitude Analyses Of The Decays Chi_C1 -> Eta Pi+ Pi- And Chi_C1 -> Eta' Pi+ Pi-, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Sep 2011

Amplitude Analyses Of The Decays Chi_C1 -> Eta Pi+ Pi- And Chi_C1 -> Eta' Pi+ Pi-, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using a data sample of 2.59 x 10^7 psi(2S) decays obtained with the CLEO-c detector, we perform amplitude analyses of the complementary decay chains chi_c1 -> eta pi+ pi- and chi_c1 -> eta' pi+ pi-. We find evidence for a P-wave eta' pi scattering amplitude, which, if interpreted as a resonance, would have exotic J^PC = 1^-+ and parameters consistent with the pi_1(1600) state reported in other production mechanisms. We also make the first observation of the decay a_0(980) -> eta' pi and measure the ratio of branching fractions B(a_0(980) -> eta' pi)/B(a_0(980) -> eta ...


Implementation And Testing Of The First Prompt Search For Electromagnetic Counterparts To Gravitational Wave Transients, Duncan Brown, J. Abadie, Stefan Ballmer, Collin Capano, P. Couvares Sep 2011

Implementation And Testing Of The First Prompt Search For Electromagnetic Counterparts To Gravitational Wave Transients, Duncan Brown, J. Abadie, Stefan Ballmer, Collin Capano, P. Couvares

Physics

Aims. A transient astrophysical event observed in both gravitational wave (GW) and electromagnetic (EM) channels would yield rich scientific rewards. A first program initiating EM follow-ups to possible transient GW events has been developed and exercised by the LIGO and Virgo community in association with several partners. In this paper, we describe and evaluate the methods used to promptly identify and localize GW event candidates and to request images of targeted sky locations. Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to Oct 20 2010), a low-latency analysis pipeline was used to identify ...


The Baryon-Dark Matter Ratio Via Moduli Decay After Affleck-Dine Baryogenesis, Scott Watson, Gordon Kane, Jing Shao, Hai-Bo Yu Sep 2011

The Baryon-Dark Matter Ratio Via Moduli Decay After Affleck-Dine Baryogenesis, Scott Watson, Gordon Kane, Jing Shao, Hai-Bo Yu

Physics

Low-scale supersymmetry breaking in string motivated theories implies the presence of O(100) TeV scale moduli, which generically lead to a significant modification of the history of the universe prior to Big Bang Nucleosynthesis. Such an approach implies a non-thermal origin for dark matter resulting from scalar decay, where the lightest supersymmetric particle can account for the observed dark matter relic density. We study the further effect of the decay on the baryon asymmetry of the universe, and find that this can satisfactorily address the problem of the over-production of the baryon asymmetry by the Affleck-Dine mechanism in the MSSM ...


Observation Of J/Ψ Pair Production In Pp Collisions At √S=7 Tev, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia Sep 2011

Observation Of J/Ψ Pair Production In Pp Collisions At √S=7 Tev, Raymond Mountain, Marina Artuso, S. Blusk, Alessandra Borgia

Physics

The production of J/\psi pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb^{-1} collected with the LHCb detector. The production cross-section for pairs with both \jpsi in the rapidity range 2


Observation Of J/Ψ Pair Production In Pp Collisions At \Sqrt{S}=7 Tev, Raymond Mountain, Marina Artuso, S. Blusk, Alesandra Borgia Sep 2011

Observation Of J/Ψ Pair Production In Pp Collisions At \Sqrt{S}=7 Tev, Raymond Mountain, Marina Artuso, S. Blusk, Alesandra Borgia

Physics

The production of J/\psi pairs in proton-proton collisions at a centre-of-mass energy of 7 TeV has been observed using an integrated luminosity of 37.5 pb^{-1} collected with the LHCb detector. The production cross-section for pairs with both \jpsi in the rapidity range 2


Observation Of The Hc(1p) Using E+E- Collisions Above Dd Threshold, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Aug 2011

Observation Of The Hc(1p) Using E+E- Collisions Above Dd Threshold, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using 586pb^-1 of e^+e^- collision data at E_CM = 4170MeV, produced at the CESR collider and collected with the CLEO-c detector, we observe the process e^+e^- --> pi^+ pi^- h_c(1P). We measure its cross section to be 15.6+-2.3+-1.9+-3.0pb, where the third error is due to the external uncertainty on the branching fraction of psi(2S) --> pi^0 h_c(1P), which we use for normalization. We also find evidence for e^+e^- --> eta h_c(1P) at 4170MeV at the 3sigma level, and see hints of a rise in the e^+e^- --> pi ...


Observation Of The H_C(1p) Using E^+E^- Collisions Above Ddbar Threshold, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Aug 2011

Observation Of The H_C(1p) Using E^+E^- Collisions Above Ddbar Threshold, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using 586pb^-1 of e^+e^- collision data at E_CM = 4170MeV, produced at the CESR collider and collected with the CLEO-c detector, we observe the process e^+e^- --> pi^+ pi^- h_c(1P). We measure its cross section to be 15.6+-2.3+-1.9+-3.0pb, where the third error is due to the external uncertainty on the branching fraction of psi(2S) --> pi^0 h_c(1P), which we use for normalization. We also find evidence for e^+e^- --> eta h_c(1P) at 4170MeV at the 3sigma level, and see hints of a rise in the e^+e^- --> pi ...


Quantum Equivalence Principle Violations In Scalar-Tensor Theories, Christian Armendariz-Picon, Riccardo Penco Aug 2011

Quantum Equivalence Principle Violations In Scalar-Tensor Theories, Christian Armendariz-Picon, Riccardo Penco

Physics

We study the equivalence principle and its violations by quantum effects in scalar-tensor theories that admit a conformal frame in which matter only couples to the spacetime metric. These theories possess Ward identities that guarantee the validity of the weak equivalence principle to all orders in the matter coupling constants. These Ward identities originate from a broken Weyl symmetry under which the scalar field transforms by a shift, and from the symmetry required to couple a massless spin two particle to matter (diffeomorphism invariance). But the same identities also predict violations of the weak equivalence principle relatively suppressed by at ...


Substrate Rigidity Deforms And Polarizes Active Gels, Shiladitya Banerjee, M. C. Marchetti Aug 2011

Substrate Rigidity Deforms And Polarizes Active Gels, Shiladitya Banerjee, M. C. Marchetti

Physics

We present a continuum model of the coupling between cells and substrate that accounts for some of the observed substrate-stiffness dependence of cell properties. The cell is modeled as an elastic active gel, adapting recently developed continuum theories of active viscoelastic fluids. The coupling to the substrate enters as a boundary condition that relates the cell's deformation field to local stress gradients. In the presence of activity, the coupling to the substrate yields spatially inhomogeneous contractile stresses and deformations in the cell and can enhance polarization, breaking the cell's front-rear symmetry.


Branching Fractions For Y(3s) -> Pi^0 H_B And Psi(2s) -> Pi^0 H_C, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Aug 2011

Branching Fractions For Y(3s) -> Pi^0 H_B And Psi(2s) -> Pi^0 H_C, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using e^+e^- collision data corresponding to 5.88M Y(3S) [25.9M psi(2S)] decays and acquired by the CLEO III [CLEO-c] detectors operating at CESR, we study the single-pion transitions from Y(3S) [psi(2S)] to the respective spin-singlet states h_{b[c]}. Utilizing only the momentum of suitably selected transition-pi^0 candidates, we obtain the upper limit B(Y(3S) -> pi^0 h_b) < 1.2\times 10^{-3} at 90% confidence level, and measure B(psi(2S) -> pi^0 h_c) = (9.0+-1.5+-1.3)\times 10^{-4}. Signal sensitivities are enhanced by excluding very asymmetric pi^0 -> gamma gamma candidates.


Branching Fractions For ϒ(3s)→ Π0hb And Ψ(2s) →Π0hc, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki Aug 2011

Branching Fractions For ϒ(3s)→ Π0hb And Ψ(2s) →Π0hc, Raymond Mountain, Marina Artuso, S. Blusk, T. Skwarnicki

Physics

Using e^+e^- collision data corresponding to 5.88M Y(3S) [25.9M psi(2S)] decays and acquired by the CLEO III [CLEO-c] detectors operating at CESR, we study the single-pion transitions from Y(3S) [psi(2S)] to the respective spin-singlet states h_{b[c]}. Utilizing only the momentum of suitably selected transition-pi^0 candidates, we obtain the upper limit B(Y(3S) -> pi^0 h_b) < 1.2\times 10^{-3} at 90% confidence level, and measure B(psi(2S) -> pi^0 h_c) = (9.0+-1.5+-1.3)\times 10^{-4}. Signal sensitivities are enhanced by excluding very asymmetric pi^0 -> gamma gamma candidates.


Semi-Leptonic D_S^+(1968) Decays As A Scalar Meson Probe, Joseph Schechter, Amir H. Fariborz, Renata Jora, M. Naeem Shahid Aug 2011

Semi-Leptonic D_S^+(1968) Decays As A Scalar Meson Probe, Joseph Schechter, Amir H. Fariborz, Renata Jora, M. Naeem Shahid

Physics

The unusual multiplet structures associated with the light spin zero mesons have recently attracted a good deal of theoretical attention. Here we discuss some aspects associated with the possibility of getting new experimental information on this topic from semi-leptonic decays of heavy charged mesons into an isosinglet scalar or pseudoscalar plus leptons.


Mcrg Minimal Walking Technicolor, Simon Catterall, Luigi Del Debbio, Joel Giedt Aug 2011

Mcrg Minimal Walking Technicolor, Simon Catterall, Luigi Del Debbio, Joel Giedt

Physics

We present a Monte Carlo renormalisation group study of the SU(2) gauge theory with two Dirac fermions in the adjoint representation. Using the two-lattice matching technique we measure the running of the coupling and the anomalous mass dimension. We find slow running of the coupling, compatible with an infrared fixed point. Assuming this running is negligible we find a vanishing anomalous dimension, gamma=-0.03(13), however taking this source of systematic error into account gives a much larger range of allowed values, -0.6 < gamma < 0.6. We also attempt to measure the anomalous mass dimension using the stability matrix method. We discuss the systematic errors affecting the current analysis and possible improvements.


Possible Z-Width Probe Of A "Brane-World" Scenario For Neutrino Masses, Joseph Schechter, Sherif Moussa, Salah Nasri, F Sannino Aug 2011

Possible Z-Width Probe Of A "Brane-World" Scenario For Neutrino Masses, Joseph Schechter, Sherif Moussa, Salah Nasri, F Sannino

Physics

The possibility that the accurately known value of the Z width might furnish information about the coupling of two neutrinos to the Majoron (Nambu-Goldstone boson of spontaneous lepton number violation) is proposed and investigated in detail. Both the "ordinary" case and the case in which one adopts a "brane" world picture with the Majoron free to travel in extra dimensions are studied. Bounds on the dimensionless coupling constants are obtained, allowing for any number of extra dimensions and any intrinsic mass scale. These bounds may be applied to a variety of different Majoron models. If a technically natural see-saw model ...