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S. Veseli

Publications and source records attributed to S. Veseli.

At least 19 recordsLinked to original sources
arXiv2019

Software Development for APS-Upgrade LLRF

An extensive service-based software system has been developed for real-time data acquisition (DAQ) on numerous subsystems of the Advanced Photon Source (APS) accelerator. The software, called DAQ, is based upon EPICS 3 Area-Detector with added EPICS 4 services, with EPICS 3 + 4 being called EPICS 7. DAQ is comprised of several network services including file storage and processing as well as numerous EPICS 7 Input-Output Controller (IOC) applications that collect data and publish to EPICS 7 from accelerator subsystems, including power supplies, diagnostics, timing, and RF systems. For the APS upgrade extensions to the DAQ software have been developed for digital Low Level RF (LLRF) systems supporting multiple hardware platforms including Lawrence Berkeley Laboratory's LLRF4 hardware and Micro Telecommunications Computing Architecture. EPICS 7 IOCs for LLRF run on multiple threads for real-time data collection, visualization , system control, and data file storage that can be triggered on accelerator beam dumps for system debug. A Python-based oscilloscope application has been developed for real-time data visualization.

physics.ins-det↗
arXiv2003

D0 Data Handling Operational Experience

We report on the production experience of the D0 experiment at the Fermilab Tevatron, using the SAM data handling system with a variety of computing hardware configurations, batch systems, and mass storage strategies. We have stored more than 300 TB of data in the Fermilab Enstore mass storage system. We deliver data through this system at an average rate of more than 2 TB/day to analysis programs, with a substantial multiplication factor in the consumed data through intelligent cache management. We handle more than 1.7 Million files in this system and provide data delivery to user jobs at Fermilab on four types of systems: a reconstruction farm, a large SMP system, a Linux batch cluster, and a Linux desktop cluster. In addition, we import simulation data generated at 6 sites worldwide, and deliver data to jobs at many more sites. We describe the scope of the data handling deployment worldwide, the operational experience with this system, and the feedback of that experience.

cs.DC↗
arXiv2003

Adapting SAM for CDF

The CDF and D0 experiments probe the high-energy frontier and as they do so have accumulated hundreds of Terabytes of data on the way to petabytes of data over the next two years. The experiments have made a commitment to use the developing Grid based on the SAM system to handle these data. The D0 SAM has been extended for use in CDF as common patterns of design emerged to meet the similar requirements of these experiments. The process by which the merger was achieved is explained with particular emphasis on lessons learned concerning the database design patterns plus realization of the use cases.

cs.DC↗
arXiv2000

Semileptonic form factors - a model-independent approach

We demonstrate that the B->D(*) l nu form factors can be accurately predicted given the slope parameter rho^2 of the Isgur-Wise function. Only weak assumptions, consistent with lattice results, on the wavefunction for the light degrees of freedom are required to establish this result. We observe that the QCD and 1/m_Q corrections can be systematically represented by an effective Isgur-Wise function of shifted slope. This greatly simplifies the analysis of semileptonic B decay. We also investigate what the available semileptonic data can tell us about lattice QCD and Heavy Quark Effective Theory. A rigorous identity relating the form factor slope difference rho_D^2-rho_A1^2 to a combination of form factor intercepts is found. The identity provides a means of checking theoretically evaluated intercepts with experiment.

hep-ph↗
arXiv1999

Distinguishing WH and WBBbar production at the Fermilab Tevatron

The production of a Higgs boson in association with a W-boson is the most likely process for the discovery of a light Higgs at the Fermilab Tevatron. Since it decays primarily to b-quark pairs, the principal background for this associated Higgs production process is WBBbar, where the BBbar pair comes from the splitting of an off mass shell gluon. In this paper we investigate whether the spin angular correlations of the final state particles can be used to separate the Higgs signal from the WBBbar background. We develop a general numerical technique which allows one to find a spin basis optimized according to a given criterion, and also give a new algorithm for reconstructing the W longitudinal momentum which is suitable for the WH and WBBbar processes.

hep-ph↗
arXiv1999

Adiabatic string shape for non-uniform rotation

It is well known that a straight Nambu-Goto string is an exact solution of the equations of motion when its end moves in a circular orbit. In this paper we investigate the shape of a confining relativistic string for a general motion of its end. We determine analytically the shape of the curved string to leading order in deviation from straightness, and show that it reduces to an expected non-relativistic result. We also demonstrate numerically that in realistic meson models this deviation is always small. We further find that the angular momentum and energy are the same as for the straight string, but that the curved string has a small radial momentum not present in a straight string. Our results justify the common assumption of straight strings usually made in hadron models.

hep-ph↗
arXiv1998

Strong radiative corrections to W b bbar production in p pbar collisions

We calculate the strong radiative corrections to the process p pbar -> W(->e nu) g^*(->b bbar). At the Tevatron this process is the largest background to the associated Higgs boson production p pbar -> W(-> e nu) H(-> b bbar). The calculation is based on the subtraction procedure, and the corrections are found to be significant.

hep-ph↗
arXiv1997

Multidimensional integration in a heterogeneous network environment

We consider several issues related to the multidimensional integration using a network of heterogeneous computers. Based on these considerations, we develop a new general purpose scheme which can significantly reduce the time needed for evaluation of integrals with CPU intensive integrands. This scheme is a parallel version of the well-known adaptive Monte Carlo method (the VEGAS algorithm), and is incorporated into a new integration package which uses the standard set of message-passing routines in the PVM software system.

physics.comp-ph↗
arXiv1997

Gluonic Hadrons and Charmless B Decays

Hybrid charmonium with mass ~4 GeV could be produced via a c c.bar color-octet component in b->c c.bar s. These states could be narrow and could have a significant branching ratio to light hadrons, perhaps enhanced by glueballs. Decays to gluonic hadrons could make a sizable contribution to B->no charm decays. Experimental signatures and search strategies are discussed.

hep-ph↗
arXiv1997

Vector boson production in hadronic collisions

We consider the production of $γ^*, W$ and $Z$ vector bosons in hadron-hadron collisions in perturbative QCD. We present results from a new numerical program which gives a full description of the production of the vector bosons and of their decay products. At small $\qt$ the calculation includes resummation of large logarithms and non-perturbative effects. The resummation is matched with the full $O(α_S)$ calculation. In addition, the program correctly reproduces the known $O(α_S)$ cross section when integrated over $\qt$. Besides presenting results for $W$ and $Z$ production at the Tevatron, we also review constraints on the non-perturbative functions using fixed target data on lepton pair production, and make several observations on this topic.

hep-ph↗
arXiv1997

On the bounds for the curvature and higher derivatives of the Isgur-Wise function

We discuss constraints imposed on the zero-recoil curvature and higher derivatives of the Isgur-Wise function by a general quark model. These constraints are expressed as bounds for a given slope parameter, and compared with those based upon analyticity properties of QCD spectral functions. Our results also indicate that in the analysis of the experimental data for semileptonic $B\rar D^{(*)}$ decays it may be important to include at least the third term in the form factor expansion about the zero recoil point.

hep-ph↗
arXiv1996

Decay constants of P and D-wave heavy-light mesons

We investigate decay constants of P and D-wave heavy-light mesons within the mock-meson approach. Numerical estimates are obtained using the relativistic quark model. We also comment on recent calculations of heavy-light pseudo-scalar and vector decay constants.

hep-ph↗
arXiv1996

Semi-leptonic B decays into higher charmed resonances

We apply HQET to semi-leptonic $B$ meson decays into a variety of excited charm states. Using three realistic meson models with fermionic light degrees of freedom, we examine the extent that the sum of exclusive single charmed states account for the inclusive semi-leptonic $B$ decay rate. The consistency of form factors with the Bjorken and Voloshin sum rules is also investigated.

hep-ph↗
arXiv1995

Fermion Confinement by a Relativistic Flux Tube

We formulate the description of the dynamic confinement of a single fermion by a flux tube. The range of applicability of this model extends from the relativistic corrections of a slowly moving quark to the ultra-relativistic motion in a heavy-light meson. The reduced Salpeter equation, also known as the no-pair equation, provides the framework for our discussion. The Regge structure is that of a Nambu string with one end fixed. Numerical solutions are found giving very good fits to heavy-light meson masses. An Isgur-Wise function with a zero recoil slope of $ξ'(1)\simeq -1.26 $ is obtained.

hep-ph↗
arXiv1995

On the validity of the reduced Salpeter equation

We adapt a general method to solve both the full and reduced Salpeter equations and systematically explore the conditions under which these two equations give equivalent results in meson dynamics. The effects of constituent mass, angular momentum state, type of interaction, and the nature of confinement are all considered in an effort to clearly delineate the range of validity of the reduced Salpeter approximations. We find that for $J\not{\hspace*{-1.0mm}=}0$ the solutions are strikingly similar for all constituent masses. For zero angular momentum states the full and reduced Salpeter equations give different results for small quark mass especially with a large additive constant coordinate space potential. We also show that $\frac{1}{m}$ corrections to heavy-light energy levels can be accurately computed with the reduced equation.

hep-ph↗
arXiv1995

S to P wave form factors in semi-leptonic B decays

We apply HQET to semi-leptonic $B$ and $B_{s}$ meson decays into the observed charmed $P$ wave states. In order to examine the sensitivity of the results to the choice of a specific model, we perform all calculations using several different meson models, and find that uncertainty introduced by the choice of a particular model is about 30\%. Specifically, assuming $τ_{B}=1.50ps$ and $V_{cb}= 0.040$, we obtain branching ratios of $(0.27\pm 0.08)\%$ and $(0.45\pm 0.14)\%$ for $B\rar D_{1}l\barν_{l}$ and $B\rar D_{2}^{*}l\barν_{l}$ decays, respectively.

hep-ph↗
arXiv1995

Radiative rare $B$ decays revisited

We reexamine contributions of higher $K$-resonances to the radiative rare decays $b\rar sγ$ in the limit where both $b$- and $s$-quark are considered heavy. Using the non-relativistic quark model, and the form factor definitions consistent with the HQET covariant trace formalism, we find significant disagreement with previous work which also used heavy quark symmetry, and excellent agreement with experimental results. In particular, the two largest fractions of the inclusive $b\rar sγ$ branching ratio are found to be $(16.8\pm 6.4)\%$ for $B\rar K^{*}(892)γ$ and $(6.2\pm 2.9)\%$ for $B\rar K_{2}^{*}(1430)γ$ decays. We also compare the contribution from the radiative decays into the eight $K$-meson states to the inclusive experimental $b\rar sγ$ mass distribution.

hep-ph↗