11483140
Heterotic string optical unification
The lower limit to string coupling unification in weakly coupled heterotic strings was shown by Kaplunovsky to be around Lambda_H ~ 5 x 10^{17} GeV. In contrast, under the scenario of an intermediate scale desert, the SU(3)_C x SU(2)_L x U(1)_Y ([321]) Minimal Supersymmetric Standard Model (MSSM) unification scale is Lambda_U ~ 2.5 x 10^{16} GeV. Optical unification was proposed by Giedt as a robust mechanism for relating these two scales. In this mechanism, intermediate scale MSSM-charged exotic particles effect running couplings like a diverging lens, always producing a ``virtual'' image of the string unification point between the string scale and the exotic particle mass scale. A heterotic string model that offers the potential to realize optical unification was recently constructed. This paper reports the initial results of an investigation into the possibility of optical unification realization in this model. This paper is a product of the NSF REU program at Baylor University and is based on a talk presented at the Second International Conference on String Phenomenology, Durham, England, 29 July - 4 August, 2003.
117261868
Symmetry and the Standard Model: Mathematics and Particle Physics
Review of Classical Physics.- A Preview of Particle Physics.- Algebraic Foundations.- First Principles and the Standard Model.- Beyond the Standard Model of Particle Physics.
12334845
Stringent phenomenological investigation into heterotic string optical unification
For the weakly coupled heterotic string (WCHS) there is a well-known factor of 20 conflict between the minimum string coupling unification scale, {lambda}{sub H}{approx}5x10{sup 17} GeV, and the projected minimal supersymmetric standard model (MSSM) gauge coupling unification scale, {lambda}{sub U}{approx}2.5x10{sup 16} GeV, assuming an intermediate scale desert (ISD). From a bottom-up approach, renormalization effects of intermediate scale MSSM-charged exotics (ISME), which are endemic to quasirealistic string models, can resolve this issue by pushing the MSSM scale up to the string scale. However, for a generic string model, this implies that the projected {lambda}{sub U} unification under the ISD assumption is accidental. If the true unification scale is {lambda}{sub H} > or approx. 5.0x10{sup 17} GeV, is it possible that an illusionary unification at {lambda}{sub U}=2.5x10{sup 17} GeV in the ISD scenario is not accidental? (This is an issue recently raised again by Binetruy et al..) Optical unification suggests that {lambda}{sub U} might not be accidental. Through its ISME constraints, optical unification offers a mechanism whereby a generic MSSM scale {lambda}{sub U}<{lambda}{sub H} is guaranteed. A WCHS model was recently constructed that could yield optical unification, depending on the availability of anomaly-cancelling D- and F-flat directions that meet optical unification ISME more » requirements. We report the results of a systematic investigation of the optical unification properties of a subset of flat directions of this model that are stringently flat. Stringent flat directions do not require significant fine-tuning and can be easily guaranteed to be F-flat to all finite order (or to at least a given finite order consistent with electroweak scale supersymmetry breaking). They are the likely roots of more complicated (and arguably, more finely tuned) flat directions. To realize optical unification, a flat direction must keep all exotic triplets and doublets massless down to an intermediate mass scale, except for three extra pairs of Higgs which must acquire MSSM (or higher) scale mass. Additionally, six out of seven pairs of exotic hypercharged non-Abelian singlets must acquire MSSM (or higher) scale mass, while the remaining pair remains massless down to the intermediate scale. Our investigation revealed that the best stringent directions could induce MSSM scale or higher mass to at most three of the six pairs of exotic singlets, and to only two out of three pairs of exotic Higgs. Each of these stringent flat directions keeps all of the exotic triplets and remaining exotic doublets massless down to an intermediate scale. Thus, some fine-tuning away from stringent flat directions is necessary, if it is possible for an additional three pairs of exotic hypercharged singlets and one more pair of extra Higgs to become MSSM scale massive. Future research may indicate if such flat directions exist. This paper is a product of the 2003-2004 NSF REU program at Baylor University. « less
16595190
Grover's Quantum Search Algorithm and Free Fermionic Heterotic Models
Given an efficient and systematic method for generating input sets for free fermionic heterotic model building we consider what the realistic bounds are for a statistical analysis of the free fermionic Landscape with a classical computer. We then consider what kind of improvement could be expected on a quantum computer. We do outline the basic structure of the relevant quantum algorithms, but we do not detail the construction of the oracle which would be involved in the calculations.
11661903
Scattering of macroscopic heterotic strings
Abstract We show that macroscopic heterotic strings, formulated as strings which wind around a compact direction of finite but macroscopic extent, exhibit non-trivial scattering at low energies. This occurs at order velocity squared and may thus be described as geodesic motion on a moduli space with a non-trivial metric which we construct. Our result is in agreement with a direct calculation of the string scattering amplitude.
126074679
The mice target
125332655
Performance of the ATLAS tau trigger with 7 TeV collision data at the LHC
Tau leptons are a fundamental ingredient in the discovery of new physics at the LHC. The reconstruction of hadronic tau decays at the trigger level, although a very challenging task in protonproton collision environments, allows us to double the sample of tau decays collected, and provides additional discovery power to final states which include tau leptons. In this contribution we show the understanding of the tau trigger system using data collected with the ATLAS detector at the LHC in proton-proton collisions at a center-of-mass energy of 7 TeV. We present the most relevant quantities used in the different stages of the trigger selection, and the trigger efficiencies as a function of ET using tau-like QCD events passing the offline reconstruction and identification selection.
122078935
The LAGUNA project: Towards the giant liquid based detectors for proton decay searches and for low energy neutrino astrophysics
Jan Kisiel Institute of Physics, University of Silesia Uniwersytecka 4, 40-007 Katowice, Poland E-mail: Jan.Kisiel@us.edu.pl D. Angusa, A. Arigab, D. Autieroc, A. Apostud, A. Badertschere, T. Bennetf, G. Bertolag, P.F. Bertolag, O. Besidah, A. Bettinii, C. Boothf, J.L. Bornec, I. Brancusd, W. Bujakowskij, J.E. Campagnec, G. Cata-Danild, F. Chipesiud, M. Chorowskik, J. Crippsf, A. Curionie, S. Davidsonc, Y.R.A Declaisc, U. Drostg, O. Duliul, J. Dumarchezc, T. Enqvistm, A. Ereditatob, F. v Feilitzschn, H. Fynboo, T. Gamblef, G. Galvaninp, A. Gendottie, W. Gizickik, M. GogerNeffn, U. Grassling, D. Gurneyq, M. Hakalar, S. Hannestado, M. Haworthq, A. Jipal, F. Jugetb, T. Kalliokoskis, S. Katsanevasc, M. Keent, I.Kreslob, V. Kudryastevf, P. Kuusiniemim, L. Labargau, T. Lachenmaiern, J.C. Lanfranchin, I. Lazanul, T. Lewken, K. Loom, P. Lightfootf, M. Lindnerv, P. Lombardiw, A. Longhinh, J. Maalampis, M. Marafinic, A. Marchionnie, R.M. Margineanud, A. Markiewiczx, T. Marrodan-Undagoitan, J.E. Marteauc, R. Matikainenr, Q. Meindln, M. Messinab, J.W. Mietelskiy, B. Mitricad, A. Mordasinig, L. Moscah, U. Moserb, G. Nuijtenr, L. Oberauern, A. Oprinad, S. Palingf, S. Pascolia, T. Patzakc, M. Pectud, Z. Pileckij, F. Piquemalc, W. Potzeln, W. Pytelx, M. Raczynskix, G. Raffeltz, G. Ranucciw, G. Ristainop, M. Robinsonf, R. Rogersq, J. Roinistor, M. Romanai, E. RondioA, B. Rossib, A. Rubbiae, Z. Sadeckix, C. Saenzi, A. Saftoiud, J. Salmelainenr, O. Simal, J. Slizowskij, K. Slizowskij, J. SobczykB, N. Spoonerf, S. Stoicad, J. Suhonens, R. SulejA, M. Szarskay, T. SzeglowskiC, M. Temussip, J. Thompsonq, L. Thompsonf, W.H. Trzaskas, M. Tippmannn, A. Tonazzoc, K. Urbanczykj, G. Vasseurh, A. Williamst, J. Wintern, K. Wojtuszewskaj, M. Wurmn, A. Zalewskay, M. Zampaoloc, M. Zitoh
2619788
Obscured and unobscured AGN populations in a hard-X-ray selected sample of the XMDS survey
Aims. Our goal is to probe the populations of obscured and unobscured AGN investigating their optical-IR and X-ray properties as a function of X-ray flux, luminosity and redshift within a hard X-ray selected sample with wide multiwavelength coverage. 
Methods. We selected a sample of 136 X-ray sources detected at a significance of ≥3σ in the 2-10 keV band (F_(2-10) ≳ 10^(-14) erg cm^(-2) s^(-1)) in a ~1 deg^2 area in the XMM Medium Deep Survey (XMDS). The XMDS area is covered with optical photometry from the VVDS and CFHTLS surveys and infrared Spitzer data from the SWIRE survey. Based on the X-ray luminosity and X-ray to optical ratio, 132 sources are likely AGN, of which 122 have unambiguous optical - IR identification. The observed optical and IR spectral energy distributions of all identified sources are fitted with AGN/galaxy templates in order to classify them and compute photometric redshifts. X-ray spectral analysis is performed individually for sources with a sufficient number of counts and using a stacking technique for subsamples of sources at different flux levels. Hardness ratios are used to estimate X-ray absorption in individual weak sources. 
Results. 70% of the AGN are fitted by a type 2 AGN or a star forming galaxy template. We group them together in a single class of "optically obscured" AGN. These have "red" optical colors and in about 60% of cases show significant X-ray absorption (N_H > 10^(22) cm^(-2)). Sources with SEDs typical of type 1 AGN have "blue" optical colors and exhibit X-ray absorption in about 30% of cases. The stacked X-ray spectrum of obscured AGN is flatter than that of type 1 AGN and has an average spectral slope of Γ = 1.6. The subsample of objects fitted by a star forming galaxy template has an even harder stacked spectrum, with Γ ~ 1.2-1.3. The obscured fraction is larger at lower fluxes, lower redshifts and lower luminosities. X-ray absorption is less common than "optical" obscuration and its incidence is nearly constant with redshift and luminosity. This implies that at high luminosities X-ray absorption is not necessarily related to optical obscuration. The estimated surface densities of obscured, unobscured AGN and type 2 QSOs are respectively 138, 59 and 35 deg^(-2) at F > 10^(-14) erg cm^(-2) s^(-1).