GUT predictions for quark and lepton mass ratios
Co-authored with Stefan Antusch; published in AIP Conf.Proc. 1200 (2010) 928-931
Group theoretical factors from GUT symmetry breaking can lead to predictions for the ratios of quark and lepton masses... more Group theoretical factors from GUT symmetry breaking can lead to predictions for the ratios of quark and lepton masses at the unification scale. Due to supersymmetric (SUSY) threshold corrections the viability of such predictions can depend strongly on the SUSY parameters. We derive possible new predictions for the GUT scale ratios m_\mu/m_s, y_\tau/y_b and y_t/y_b and compare them with the experimentally allowed ranges for three common SUSY breaking scenarios.
Download (.1520v1)Measurement of the Properties of the top Quark at DØ
To appear in the Proceedings of the
XIX. International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2011, April 11-15, Newport News, USA)
Different measurements of the properties of the top quark using up to $5.4 fb^{-1}$ collected with the D{\O} detector... more Different measurements of the properties of the top quark using up to $5.4 fb^{-1}$ collected with the D{\O} detector at the Fermilab Tevatron collider are presented. The top mass is obtained from a study of dilepton and lepton+jets final states, while the width is obtained from a combination of the measurements of the single top production via t-channel exchange and the determination of the t \rightarrow Wb branching ratio. Furthermore the measurement of the helicity of the W boson from top quark decays, a measurement of $t\bar{t}$ spin correlations and a measurement of the jet pull (color flow) in $t\bar{t}$ events are presented.
D* production in deep-inelastic scattering at low Q^2
To appear in the Proceedings of the DIS2011 conference held in Virginia, USA.
Inclusive production of D* mesons in deep-inelastic scattering at HERA is studied in the range 5 < Q^2 < 100... more
Inclusive production of D* mesons in deep-inelastic scattering at HERA is studied in the range 5 < Q^2 < 100 GeV^2 of the photon virtuality and 0.02 < y < 0.70 of the inelasticity of the scattering process. The visible range for the D* meson is pT (D*) > 1.25 GeV and |h(D*)| < 1.8.
The data were taken with the H1 detector in the years 2004 to 2007 and correspond to an integrated luminosity of 347 pb^−1. Single and double differential cross sections are measured. The results are compared to QCD predictions.
Top differential cross section measurements (Tevatron)
To appear in the Proceedings of TOP2011, 4th International Workshop on Top Quark Physics, Spain, 2011
Differential cross sections in the top quark sector measured at the Fermilab Tevatron collider are presented. CDF used... more Differential cross sections in the top quark sector measured at the Fermilab Tevatron collider are presented. CDF used 2.7 fb$^{-1}$ of data and measured the differential cross section as a function of the invariant mass of the $t\bar{t}$ system. The measurement shows good agreement with the standard model and furthermore is used to derive limits on the ratio $\kappa /M_{Pl}$ for gravitons which decay to top quarks in the Randall-Sundrum model. D0 used 1.0 fb$^{-1} of data to measure the differential cross section as a function of the transverse momentum of the top quark. The measurement shows a good agreement to the higher order perturbative QCD prediction and various predictions based on various Monte-Carlo generators.
Massive Spin-2 States as the Origin of the Top Quark Forward-Backward Asymmetry
We show that the anomalously large top quark forward-backward asymmetry observed by CDF and D\O\, can naturally be... more We show that the anomalously large top quark forward-backward asymmetry observed by CDF and D\O\, can naturally be accommodated in models with flavor-violating couplings of a new massive spin-2 state to quarks. Regardless of its origin, the lowest-order couplings of a spin-2 boson to fermions are analogous to the coupling of the graviton to energy/momentum, leading to strong sensitivity of the effects associated with its virtual exchange to the energy scales at hand. Precisely due to this fact, the observed dependence of the asymmetry on the $t\bar t$ invariant mass fits nicely into the proposed framework. In particular, we find a vast parameter space which can lead to the central value for the observed forward-backward asymmetry in the high mass bin, while being in accord with all of the existing experimental constraints.
Optimizing Track Reconstruction in NOvA
A review of the work I did at the University of Minnesota as a part of the NSF REU program in physics. This paper was my senior thesis for my undergraduate degree in physics at Concordia College, Moorhead.
New track analysis software has been created to test and optimize particle tracking algorithms. The new software... more
New track analysis software has been created to test and optimize particle tracking algorithms. The new software allows for optimization of the Kalman lter used in the recent tracking algorithm KalmanTrack and gives an idea of the experimental
error due to tracking. The new analysis software, KalmanTrackAna, uses Monte Carlo simulation to test track recognition and estimates goodness of t. We conclude that KalmanTrackAna can be used to optimize the algorithm, but that the current algorithm is insucient. Points of emphasis in further work are identi ed such non-linear tracks. Further, we note that much work is left before the particle trajectory reconstruction
software is complete.
Top quark physics at the LHC
In this contribution we shall present the results about the physics of the top quark by CERN’s ATLAS and CMS... more In this contribution we shall present the results about the physics of the top quark by CERN’s ATLAS and CMS experiments. After a brief motivation of why it is important to study the top quark at the LHC, we shall discuss the measurement of the production cross sections of top pairs and single tops. Then, we shall present an overview its properties: mass, flavour-changing neutral currents (FCNC), anomalous ETmiss, resonances and charge asymmetry. The overall agreement with the Standard Model predictions is very good.
Black Hole Remnants at the LHC
L. Bellagamba, R. Casadio, R. Di Sipio, V. Viventi
We investigate possible signatures of black hole events at the LHC in the hypothesis that such objects will not... more We investigate possible signatures of black hole events at the LHC in the hypothesis that such objects will not evaporate completely, but leave a stable remnant. For the purpose of defining a reference scenario, we have employed the publicly available Monte Carlo generator CHARYBDIS2, in which the remnant's behavior is mostly determined by kinematic constraints and conservation of some quantum numbers, such as the baryon charge. Our findings show that electrically neutral remnants are highly favored and a significantly larger amount of missing transverse momentum is to be expected with respect to the case of complete decay.
Higgs Boson Mass Predictions in SUGRA Unification and Recent LHC-7 Results
by Sujeet Akula
LHC-7 has narrowed down the mass range of the light Higgs boson. This result is consistent with the supergravity... more LHC-7 has narrowed down the mass range of the light Higgs boson. This result is consistent with the supergravity unification framework and the current Higgs boson mass window implies a rather significant loop correction to the tree value pointing to a relatively heavy scalar sparticle spectrum with universal boundary conditions. It is shown that the largest value of the Higgs boson mass is obtained on the Hyperbolic Branch of radiative breaking. The implications of light Higgs boson in the broader mass range of 115 GeV to 131 GeV and a narrower range of 123 GeV to 127 GeV are explored in the context of the discovery of supersymmetry at LHC-7 and for the observation of dark matter in direct detection experiments.
Naturalness, Supersymmetry and Implications for LHC and Dark Matter
by Sujeet Akula
Submitted for publication
It is shown that the Hyperbolic Branch of the radiative electroweak symmetry breaking contains in it three regions:... more It is shown that the Hyperbolic Branch of the radiative electroweak symmetry breaking contains in it three regions: the Focal Point, Focal Curves, and Focal Surfaces. Further, the Focal Point is shown to lie on the boundary of a Focal Curve. These focal regions allow for a small $\mu$ while scalar masses can become large and may lie in the several TeV region. It is shown that for the mSUGRA model the current LHC-7 constraint depletes the Focal Point region while regions on Focal Curves and Focal Surfaces remain largely intact. The LHC implications for models which lie on Focal Curves are briefly discussed as well as the implications of dark matter constraints for the Focal Point, Focal Curves and Focal Surfaces are discussed.
Excess Observed in CDF $B^0_s \to μ^{+} μ^{-}$ and SUSY at the LHC
by Sujeet Akula
Published in Phys. Rev. D 84, 115011 (2011)
The recent excess observed by CDF in $B^0_s \to \mu^{+} \mu^{-}$ is interpreted in terms of a possible supersymmetric... more The recent excess observed by CDF in $B^0_s \to \mu^{+} \mu^{-}$ is interpreted in terms of a possible supersymmetric origin. An analysis is given of the parameter space of mSUGRA and non-universal SUGRA models under the combined constraints from LHC-7 with 165 pb$^{-1}$ of integrated luminosity, under the new XENON-100 limits on the neutralino-proton spin independent cross section and under the CDF $B^0_s \to \mu^{+} \mu^{-}$ 90% C.L. limit reported to arise from an excess number of dimuon events. It is found that the predicted value of the branching ratio $B^0_s \to \mu^{+} \mu^{-}$ consistent with all the constraints contains the following set of NLSPs: chargino, stau, stop or CP odd (even) Higgs. The lower bounds of sparticles, including those from the LHC, XENON and CDF $B^0_s\to \mu^+\mu^-$ constraint, are exhibited and the shift in the allowed range of sparticle masses arising solely due to the extra constraint from the CDF result is given. It is pointed out that the two sided CDF 90% C.L. limit puts upper bounds on sparticle masses. An analysis of possible signatures for early discovery at the LHC is carried out corresponding to the signal region in $B^0_s \to \mu^{+} \mu^{-}$. Implications of GUT-scale non-universalities in the gaugino and Higgs sectors are discussed. If the excess seen by the CDF Collaboration is supported by further data from LHCb or D0, this new result could be a harbinger for the discovery of supersymmetry.
Hopf maps and Wigner's little groups
Co-authored with Ruben Mkrtchyan and Armen Nersessian
We present the explicit formulae relating Hopf maps with Wigner’s little groups. They, particularly, explain simple... more We present the explicit formulae relating Hopf maps with Wigner’s little groups. They, particularly, explain simple action of group on a fiber for the first and second Hopf fibrations, and present most simplified form for the third one. Corresponding invariant Lagrangians are presented, and their possible reductions are discussed.
Action-angle variables for dihedral systems on the circle
Co-authored with Olaf Lechtenfeld, Armen Nersessian, published in Physics Letters A 374 (2010) 4647–4652
A nonrelativistic particle on a circle and subject to a cos^{-2}(k phi) potential is related to the two-dimensional... more A nonrelativistic particle on a circle and subject to a cos^{-2}(k phi) potential is related to the two-dimensional (dihedral) Coxeter system I_2(k), for k in N. For such `dihedral systems' we construct the action-angle variables and establish a local equivalence with a free particle on the circle. We perform the quantization of these systems in the action-angle variables and discuss the supersymmetric extension of this procedure. By allowing radial motion one obtains related two-dimensional systems, including A_2, BC_2 and G_2 three-particle rational Calogero models on R, which we also analyze.
Quantum ring models and action-angle variables
Co-authored with Stefano Bellucci, Armen Nersessian and Armen Saghatelian
We suggest to use the action-angle variables for the study of properties of (quasi)particles in quantum
rings.... more
We suggest to use the action-angle variables for the study of properties of (quasi)particles in quantum
rings. For this purpose we present the action-angle variables for three two-dimensional singular oscillator
systems. The first one is the usual (Euclidean) singular oscillator, which plays the role of the confinement
potential for the quantum ring. We also propose two singular spherical oscillator models for the role of
the confinement system for the spherical ring. The first one is based on the standard Higgs oscillator
potential. We show that, in spite of the presence of a hidden symmetry, it is not convenient for the study
of the system’s behaviour in a magnetic field. The second model is based on the so-called CP1 oscillator
potential and respects the inclusion of a constant magnetic field.
Second Hopf map and Yang-Coulomb system on 5d (pseudo)sphere
Co-authored with Stefano Bellucci, Francesco Toppan, published in J.Phys.A43:045205,2010
Using the second Hopf map, we perform the reduction of the eight-dimensional (pseudo)spherical (Higgs)oscillator to a... more Using the second Hopf map, we perform the reduction of the eight-dimensional (pseudo)spherical (Higgs)oscillator to a five-dimensional system interacting with a Yang monopole. Then, using a standard trick, we obtain, from the latter system, the pseudospherical and spherical generalizations of the Yang-Coulomb system (the five dimensional analog of MICZ-Kepler system). We present the whole set of its constants of motions, including the hidden symmetry generators given by the analog of Runge-Lenz vector. In the same way, starting from the eight-dimensional anisotropic inharmonic Higgs oscillator, we construct the integrable (pseudo)spherical generalization of the Yang-Coulomb system with the Stark term.
Second Hopf map and supersymmetric mechanics with Yang monopole
Co-authored with M. Gonzales, Z. Kuznetsova, A. Nersessian, F. Toppan, published in Phys.Rev.D80:025022,2009
We propose to use the second Hopf map for the reduction (via SU(2) group action) of the eight-dimensional N=8... more We propose to use the second Hopf map for the reduction (via SU(2) group action) of the eight-dimensional N=8 supersymmetric mechanics to five-dimensional supersymmetric systems specified by the presence of an SU(2) Yang monopole. For our purpose we develop the relevant Lagrangian reduction procedure. The reduced system is characterized by its invariance under the N=5 or N=4 supersymmetry generators (with or without an additional conserved BRST charge operator) which commute with the su(2) generators.
Multicenter Higgs Oscillators and Calogero Model
Published in Phys.Atom.Nucl.73:579-582,2010
We show that the spherical part of N-particle Calogero model describes, after exclusionof the center of mass, the... more
We show that the spherical part of N-particle Calogero model describes, after exclusionof the center of mass, the motion of the particle on (N − 2)-dimensional sphere interacting withN(N − 1)/2 force centers with Higgs oscillator potential. In the case of four-particle system these force centers are located at the
vertexes of cuboctahedron. The geometry of the five-particle case is also investigated.
Dipole transitions and Stark effect in the charge-dyon bound system
Co-authored with L.Mardoyan, A.Nersessian, H.Sarkisyan published in J. Phys.A40 (2007), 5973-5980
We consider the dipole transitions and the linear and quadratic Stark effect in the MICZ-Kepler system interpreting as... more We consider the dipole transitions and the linear and quadratic Stark effect in the MICZ-Kepler system interpreting as a charge-dyon system. We show, that while the linear Stark effect in the ground state is proportional to azimuth quantum number(and to the sign of monopole number), the quadratic Stark effect in the ground state is independent on the signs of azimuth and monopole numbers.