377 Matching Results

Search Results

Advanced search parameters have been applied.

New charm results from FOCUS

Description: New results from the photoproduction experiment FOCUS are reported: Dalitz plot analysis, semileptonic form factor ratios and excited meson spectroscopy. The author reports on three new results from the photoproduction experiment FOCUS: the first Dalitz plot analysis of charm meson decays using the K-matrix approach[ 1], new measurements of the D{sub s}{sup +} {yields} {delta}(1020) {mu}{sup +}{nu} form factor ratios [2], and new measurements on L=1 excited meson spectroscopy [3], i.e., precise measurements of the masses and widths of the D*{sub 2}{sup +} and D*{sub 2}{sup 0} mesons, and evidence for broad states decaying to D{sup +}{pi}{sup -}, D{sup 0}{pi}{sup +} (the first such evidence in D{sup 0}{pi}{sup +}). The data for this paper were collected in the Wideband photoproduction experiment FOCUS during the Fermilab 1996-1997 fixed-target run.
Date: December 1, 2004
Creator: Bianco, Stefano & /Frascati
Partner: UNT Libraries Government Documents Department

Contraints on New Physics in MFV models: a model-independent analysis of \DeltaF=1 processes

Description: We analyze the constraints on dimension-six {Delta}F = 1 effective operators in models respecting the MFV hypothesis, both in the one-Higgs doublet case and in the two-Higgs doublet scenario with large tan {beta}. The constraints are derived mainly from the b {yields} s inclusive observables measured at the B factories. The implications of these bounds in view of improved measurements in exclusive and inclusive observables in b {yields} s{ell}{sup +}{ell}{sup -} and s {yields} d{nu}{bar {nu}} transitions are discussed.
Date: November 5, 2008
Creator: Hurth, Tobias; /SLAC, /CERN; Isidori, Gino; /Pisa, Scuola Normale Superiore /INFN, Pisa /Frascati; Kamenik, Jernej F.; /Frascati /Stefan Inst., Ljubljana et al.
Partner: UNT Libraries Government Documents Department

Longitudinal Beam Stability in the SUPER B-FACTORY

Description: We give an overview of wake fields and impedances in a proposed Super B project, which is based on extremely low emittance beams colliding at a large angle with a crab waist transformation. Understanding the effects that wake fields have on the beam is critical for a successful machine operation. We use our combined experience from the operation of the SLAC B-factory and DA{Phi}NE {Phi}-factory to eliminate strong HOM sources and minimize the chamber impedance in the Super B design. Based on a detailed study of the wake fields in this design we have developed a quasi-Green's function for the entire ring that is used to study bunch lengthening and beam stability. In particular, we check the stability threshold using numerical solutions of the Fokker-Plank equation. We also make a comparison of numerical simulations with the bunch lengthening data in the B- factory.
Date: July 6, 2009
Creator: Novokhatski, A.; /SLAC; Zobov, M. & /Frascati
Partner: UNT Libraries Government Documents Department

Betatron-Function Measurement in Lattices with 90-Degrees Sections

Description: Lattice functions derived from betatron phase-advance measurements have been used successfully at many e{sup +}-e{sup -} facilities in the world, including at the PEP-II High Energy Ring. For the Low energy Ring of PEP-II, however, extraction of meaningful beta functions is hampered by the 90{sup o} phase advance/cell in the arcs, which causes a singularity in the expressions for beta. An algorithm has been developed calculating beta functions based on {beta} and {alpha} at the beginning of an arc and tracking the Twiss parameters through the arc while matching the observed phase advance/cell. Stability of the algorithm is improved by doing the same calculation 'backward' as well as forward and averaging the result. The algorithm allows estimating beta functions at bad BPMs in many cases. The paper presents the algorithm used as well as examples of use in PEP.
Date: April 24, 2012
Creator: Wienands, U.; /SLAC; Biagini, M.E. & /Frascati
Partner: UNT Libraries Government Documents Department

Emittance Adapter for a Diffraction Limited Synchrotron Radiation Source

Description: We investigate the possibility of reaching very small horizontal and vertical emittances inside an undulator in a storage ring, by means of a local exchange of the apparent horizontal and vertical emittances, performed with a combination of skew quadrupoles and one solenoid in a dedicated insertion line in the storage ring. The insertion leaves the ring parameters and its optical properties unaffected. This scheme could greatly relax the emittance requirements for a diffraction limited synchrotron light source. The lattice derivation and design is described.
Date: March 1, 2012
Creator: Chao, Alexander Wu; /SLAC; Raimondi, Pantaleo & /Frascati
Partner: UNT Libraries Government Documents Department

Beam-Beam Simulations for a Single Pass SuperB-Factory

Description: A study of beam-beam collisions for an asymmetric single pass SuperB-Factory is presented [1]. In this scheme an e{sup -} and an e{sup +} beam are first stored and damped in two Damping Rings (DR), then extracted, compressed and focused to the IP. After collision the two beams are re-injected in the DR to be damped and extracted for collision again. The explored beam parameters are similar to those used in the design of the International Linear Collider, except for the beam energies. Flat beams and round beams were compared in the simulations in order to optimize both luminosity performances and beam blowup after collision. With such approach a luminosity of the order of 10{sup 36} cm{sup -2} s{sup -1} can be achieved.
Date: May 18, 2007
Creator: Biagini, M.E.; /Frascati; Raimondi, P.; Seeman, J.; /SLAC; Schulte, D. et al.
Partner: UNT Libraries Government Documents Department

Status of the observed and predicted b anti-b production at the Tevatron

Description: The authors review the experimental status of the b-quark production at the Fermilab Tevatron. They compare all available measurements to perturbative QCD predictions (NLO and FONLL) and also to the parton-level cross section evaluated with parton-shower Monte Carlo generators. They examine both the single b cross section and the so called b{bar b} correlations. The review shows that the experimental situation is quite complicated because the measurements appear to be inconsistent among themselves. In this situation, there is no solid basis to either claim that perturbative QCD is challenged by these measurements or, in contrast, that long-standing discrepancies between data and theory have been resolved by incrementally improving the measurements and the theoretical prediction.
Date: September 1, 2005
Creator: Happacher, F.; Giromini, P.; /Frascati; Ptohos, F. & U., /Cyprus
Partner: UNT Libraries Government Documents Department

Recent Observations on a Horizontal Instability in the DAFNE Positron Ring

Description: A strong horizontal instability limits the maximum positron current storable in the DAFNE Phi-Factory. A powerful feedback system makes it possible to store and put in collision more than 1300 mA of positron current in 105-109 bunches. Nevertheless, a much higher current (>2.4A) has been successfully stored in the twin electron ring. Measurements have been carried out to understand the positron current limit and to characterize the behavior of the horizontal instability at high current with different bunch patterns. Grow/damp turn-by-turn data obtained by turning off the horizontal feedback have been acquired and analyzed. Spectral analysis and growth rates of the instability are shown. In particular, the -1 mode has strong evidence and fast growth rate. Its growth rate behavior is analyzed at different beam currents and bunch patterns.
Date: January 20, 2006
Creator: Drago, A.; Zobov, M.; /Frascati; Teytelman, D. & /SLAC
Partner: UNT Libraries Government Documents Department

Longitudinal Bunch Position Control for the Super-B Accelerator

Description: The use of normal conducting cavities and an ion-clearing gap will cause a significant RF accelerating voltage gap transient and longitudinal phase shift of the individual bunches along the bunch train in both rings of the SuperB accelerator. Small relative centroid position shifts between bunches of the colliding beams will have a large adverse impact on the luminosity due to the small {beta}*{sub y} at the interaction point (IP). We investigate the possibility of minimizing the relative longitudinal position shift between bunches by reducing the gap transient in each ring and matching the longitudinal bunch positions of the two rings at the IP using feedback/feedforward techniques in the LLRF. The analysis is conducted assuming maximum use of the klystron power installed in the system.
Date: May 15, 2009
Creator: Bertsche, Kirk; Rivetta, Claudio; Sullivam, Michael K.; /SLAC; Drago, Alessandro & /Frascati
Partner: UNT Libraries Government Documents Department

Multibunch feedback: Strategy, technology and implementation options

Description: The proposed next generation accelerator and synchrotron light facilities will require active feedback systems to control multi-bunch instabilities. These feedback systems must operate in machines with thousands of circulating bunches and with short (2--4 ns) interbunch intervals. The functional requirements for transverse (betatron) and longitudinal (synchrotron) feedback systems are presented. Several possible implementation options are discussed and system requirements developed. Results are presented from a digital signal processing based synchrotron oscillation damper operating at the SSRL/SLAC SPEAR storage ring.
Date: October 1, 1992
Creator: Fox, J.D.; Eisen, N.; Hindi, H.; Oxoby, G.; Sapozhnikov, L.; Linscott, I. (Stanford Univ., CA (United States)) et al.
Partner: UNT Libraries Government Documents Department

Klystron Linearizer for Use with 1.2 MW 476 MHz Klystrons in PEP-II RF Systems

Description: The direct and comb loop feedback around the RF cavities in PEP-II is critical in reducing longitudinal instabilities driven by the cavity impedance. The non-linear 1.2 MW klystron is in the signal path for these feedback loops. As a result, the effective small-signal gain of the klystron at 85% saturation reduces the impedance control by factors of 5 to 20 as compared to a linear power amplifier. A klystron linearizer circuit has been developed which operates in series with the power amplifier and acts to equalize the small and large signal gains through the combination. The technique must implement a 1 MHz linear control bandwidth over roughly 15 dB of RF signal level variation. The dynamics of this system is operating point dependent, and the channel must have dynamic gain compensation to keep the linearity compensation loop stable over changes in operating point. The design of this non-linear signal processing channel (incorporating RF and DSP techniques) and measured results from full-power klystron testing are presented.
Date: June 15, 2005
Creator: Fox, J.; Mastorides, T.; Teytelman, D.; Van Winkle, D.; Zhou, Y.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Absolute Bunch Length Measurements at the ALS by Incoherent Synchrotron Radiation Fluctuation Analysis

Description: By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.
Date: January 24, 2008
Creator: Filippetto, D.; /Frascati; Sannibale, F.; Zolotorev, Max Samuil; /LBL, Berkeley; Stupakov, G.V. et al.
Partner: UNT Libraries Government Documents Department

A 90-GHz Photoinjector

Description: Photocathode rf guns depend on mode locked laser systems to produce an electron beam at a given phase of the rf. In general, the laser pulse is less than {sigma}{sub z} = 10{sup o} of rf phase in length and the required stability is on the order of {Delta}{phi} = 1{sup o}. At 90 GHz (W-band), these requirements correspond to {sigma}{sub z} = 333 fsec and {Delta}{phi} = 33 fsec. Laser system with pulse lengths in the fsec regime are commercially available, the timing stability is a major concern. We propose a multi-cell W-band photoinjector that does not require a mode locked laser system. Thereby eliminating the stability requirements at W-band. The laser pulse is allowed to be many rf periods long. In principle, the photoinjector can now be considered as a thermionic rf gun. Instead of using an alpha magnet to compress the electron bunch, which would have a detrimental effect on the transverse phase space quality due to longitudinal phase space mixing, we propose to use long pulse laser system and a pair of undulators to produce a low emittance, high current, ultra-short electron bunch for beam dynamics experiments in the 90 GHz regime.
Date: September 12, 2005
Creator: Palmer, D.T.; Hogan, M.J.; /SLAC; Ferrario, M.; Serafini, L. & /Frascati /INFN, Milan
Partner: UNT Libraries Government Documents Department

SuperB Bunch-By-Bunch Feedback R&D

Description: The SuperB project has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. The SuperB design is based on collisions with extremely low vertical emittance beams and high beam currents. A source of emittance growth comes from the bunch by bunch feedback systems producing high power correction signals to damp the beams. To limit any undesirable effect, a large R&D program is in progress, partially funded by the INFN Fifth National Scientific Committee through the SFEED (SuperB Feedback) project approved within the 2010 budget. The SuperB project [1] has the goal to build in Italy, in the Frascati or Tor Vergata area, an asymmetric e{sup +}/e{sup -} Super Flavor Factory to achieve a peak luminosity > 10**36 cm{sup -2} s{sup -1}. In the last and current years, the machine layout has been deeply modified, in particular the main rings are now shorter and an option with high currents has been foreseen. In the fig.1 the new SuperB layout is shown. From bunch-by-bunch feedback point of view, the simultaneous presence in the machine parameters, of very low emittance, of the order of 5-10 pm in the vertical plane, and very high currents, at level of 4 Ampere for the Low Energy Ring, asks for designing very carefully the bunch-by-bunch feedback systems. The parameter list is presented in Fig. 2. The bunch-by-bunch feedback design must take care of the risky and exciting challenges proposed in the SuperB specifications, but it should consider also some other important aspects: flexibility in terms of being able to cope to unexpected beam behaviours [2], [3] legacy of previous version experience [4], [5] and internal powerful diagnostics [6] as in the systems previously used ...
Date: August 12, 2011
Creator: Drago, A.; Beretta, M.; /Frascati; Bertsche, K.; Novokhatski, A.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Optimization of Chromatic Optics Near the Half Integer in PEP-II

Description: The PEP-II collider has benefited greatly from the correction of the chromatic functions. By optimizing sextupole family strengths, it is possible to correct the non-linear chromaticity, the chromatic beta, and the second order dispersion in both the LER and HER. Having implemented some of these corrections, luminosity was improved in PEP-II by almost 10%.
Date: November 6, 2007
Creator: Yocky, G.; Cai, Y.; Decker, F.J.; Nosochkov, Y.; Wienands, U.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

A Preliminary Interaction Region Design for a Super B-Factory

Description: The success of the two B-Factories (PEP-II and KEKB) has encouraged us to look at design parameters for a B-Factory with a 30-50 times increase in the luminosity of the present machines to a luminosity of L {approx} 1 x 10{sup 36} cm{sup -2} sec{sup -1}. We present an initial design of an interaction region for a ''SuperB'' accelerator with a crossing angle of {+-}14 mrad and include a discussion of the constraints, requirements and concerns that go into designing an interaction region for these very high luminosity e{sup +}e{sup -} machines.
Date: June 10, 2005
Creator: Sullivan, M.; Donald, M.; Ecklund, S.; Novokhatski, A.; Seeman, J.; Wienands, U. et al.
Partner: UNT Libraries Government Documents Department

A Proposed Fast Luminosity Feedback for the Super-B Accelerator

Description: We present a possible design for a fast luminosity feedback for the SuperB Interaction Point (IP). The design is an extension of the fast luminosity feedback installed on the PEP-II accelerator. During the last two runs of PEP-II and BaBar (2007-2008), we had an improved luminosity feedback system that was able to maintain peak luminosity with faster correction speed than the previous system. The new system utilized fast dither coils on the High-Energy Beam (HEB) to independently dither the x position, the y position and the y angle at the IP, at roughly 100 Hz. The luminosity signal was then read out with three independent lock-in amplifiers. An overall correction was computed based on the lock-in signal strengths and beam corrections for position in x and y and in the y angle at the IP were simultaneously applied to the HEB. With the 100 times increase in luminosity for the SuperB design, we propose using a similar fast luminosity feedback that can operate at frequencies between DC and 1 kHz, high enough to follow any beam motion from the final focusing magnets.
Date: May 15, 2009
Creator: Bertsche, Kirk; Field, R.Clive; Fisher, Alan; Sullivan, Michael; /SLAC; Drago, Alessandro et al.
Partner: UNT Libraries Government Documents Department

Touschek Background and Lifetime Studies for the SuperB Factory

Description: The novel crab waist collision scheme under test at the DA{Phi}NE Frascati {Phi}-factory finds its natural application to the SuperB project, the asymmetric e{sup +}e{sup -} flavour factory at very high luminosity with relatively low beam currents and reduced backgrounds. The SuperB accelerator design requires a careful choice of beam parameters to reach a good trade-off between different effects. We present here simulation results for the Touschek backgrounds and lifetime obtained for both the low and high energy rings for different machine designs. A first set of horizontal collimators has been studied to stop Touschek particles. A study of the distributions of the Touschek particle losses at the interaction region into the detectors for further investigations is underway.
Date: August 26, 2010
Creator: Boscolo, M.; Biagini, M.; Raimondi, P.; /Frascati; Sullivan, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Phenomenological study of the atypical heavy flavor production observed at the Fermilab Tevatron

Description: The authors address known discrepancies between the heavy flavor properties of jets produced at the Tevatron collider and the prediction of conventional-QCD simulations. In this study, they entertain the possibility that these effects are real and due to new physics. They show that all anomalies can be simultaneously fitted by postulating the additional pair production of light bottom squarks with a 100% semileptonic branching fraction.
Date: November 1, 2005
Creator: Apollinari, G.; Barone, M.; Fiori, I.; Giromini, P.; Happacher, F.; Miscetti, S. et al.
Partner: UNT Libraries Government Documents Department

An Improved Design for a Super-B Interaction Region

Description: We present an improved design for a Super-B interaction region. The new design attempts to minimize the bending of the two colliding beams which results from shared magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 34 mrad to 50 mrad and the distance from the IP to the first quadrupole is increased. Although the two beams still travel through this shared magnet, these changes allow for a new magnetic field design with a septum which gives the magnet two magnetic centers. This greatly reduces the beam bending from this shared quadrupole and thereby reduces the radiative bhabha background for the detector as well as any beam emittance growth from the bending. We describe the new design for the interaction region.
Date: July 25, 2008
Creator: Sullivan, M.K.; Seeman, J.; Wienands, U.; /SLAC; Bettoni, S.; /CERN et al.
Partner: UNT Libraries Government Documents Department

Vibration Budget for SuperB

Description: We present a vibration budget for the SuperB accelerator. We include ground motion data, motion sensitivity of machine components, and beam feedback system requirements. The SuperB accelerator design attains at least 50 times higher than current B-factories due to smaller beam sizes and a crabbed waist crossing angle scheme at the IP (interaction point). The beam size (1{sigma}) at the IP will be about 10 {micro}m (horizontal) by 40 nm (vertical). These small beam sizes will make the luminosity very sensitive to mechanical vibration and electrical noise. Relative vertical misalignment of the two beams at the IP by only 8 nm will result in a 1% reduction in luminosity. The corresponding horizontal alignment tolerance of is 250x looser (2 {micro}m). The vertical beam angle at the IP for a 1% luminosity loss is fairly loose at 200 {micro}rad, and the horizontal beam angle tolerance is looser still. We will focus on vertical beam position at the IP, since this presents the greatest alignment challenge. The values presented here are for a closed orbit with tunes near a half-integer in the SuperB v.12 lattice.
Date: April 5, 2011
Creator: Bertsche, K; Wittmer, W.; /SLAC; Bolzon, B.; Brunetti, L.; Jeremie, A. et al.
Partner: UNT Libraries Government Documents Department

Parameters for a Super-Flavor-Factory

Description: A Super Flavor Factory, an asymmetric energy e{sup +}e{sup -} collider with a luminosity of order 10{sup 36} cm{sup -2} s{sup -1}, can provide a sensitive probe of new physics in the flavor sector of the Standard Model. The success of the PEP-II and KEKB asymmetric colliders in producing unprecedented luminosity above 10{sup 34} cm{sup -2} s{sup -1} has taught us about the accelerator physics of asymmetric e{sup +}e{sup -} collider in a new parameter regime. Furthermore, the success of the SLAC Linear Collider and the subsequent work on the International Linear Collider allow a new Super-Flavor collider to also incorporate linear collider techniques. This note describes the parameters of an asymmetric Flavor-Factory collider at a luminosity of order 10{sup 36} cm{sup -2} s{sup -1} at the Y(4S) resonance and about 10{sup 35} cm{sup -2} s{sup -1} at the {tau} production threshold. Such a collider would produce an integrated luminosity of about 10,000 fb{sup -1} (10 ab{sup -1}) in a running year (10{sup 7} sec) at the Y(4S) resonance. In the following note only the parameters relative to the Y(4S) resonance will be shown, the ones relative to the lower energy operations are still under study.
Date: June 27, 2006
Creator: Seeman, J.T.; Cai, Y.; Ecklund, S.; Novokhatski, A.; Seryi, A.; Sullivan, M. et al.
Partner: UNT Libraries Government Documents Department

The dipion mass spectrum in e+e- annihilation and tau decay: Isospin symmetry breaking effects from the (rho, omega, phi) mixing

Description: A way to explain the puzzling difference between the pion form factor as measured in e{sup +}e{sup -} annihilations and in {tau} decays is discussed. We show that isospin symmetry breaking, beside the already identified effects, produces also a full mixing between the {rho}{sup 0}, {omega} and {phi} mesons which generates an isospin 0 component inside the {rho}{sup 0} meson. This effect, not accounted for in current treatments of the problem, seems able to account for the apparent mismatch between e{sup +}e{sup -} and {tau} data below the {phi} mass.
Date: January 1, 2008
Creator: Benayoun, M.; David, P.; Del Buono, L.; /Paris U., VI-VII; Leitner, O.; /Paris U., VI-VII /Frascati et al.
Partner: UNT Libraries Government Documents Department