341 Matching Results

Search Results

Advanced search parameters have been applied.

Absolute Decay Rate from K<sub>2</sub><sup>0</sup>→π<sup>+</sup> + π<sup>-</sup> + π<sup>0</sup> and the barDELTA I over→bar = 1/2 Rule

Description: In this letter the author describes a measurement of the absolute decay rate {Gamma}{sub 2}({+-}0) {approx_equal} {Gamma}(K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}). The result is based on 16 events of the type {pi}{sup -} p {yields} {Lambda}K{sup 0} followed by {Lambda} {yields} p{pi}{sup -} and K{sub 2}{sup 0} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup 0}, and 2608 double-vec events {pi}{sup -} p {yields} {Lambda}K{sup 0} with {Lambda} {yields} p{pi}{sup -} and K{sub 1}{sup 0} {yields} {pi}{sup +}{pi}{sup -}.
Date: February 4, 1964
Creator: Stern, Donald; Binford, Thomas O.; Lind, V. Gordon; Anderson, Jared A.; Crawford, Jr, Frank S. & Golden, Robert L.
Partner: UNT Libraries Government Documents Department


Description: A free-surface centrifugal pump, incorporating a hydraulic bearing running in sodium, was operated at the conditions required for service in the Hallam Power Reactor. After difficulties arising from inadequate shaft clearances were alleviated, the pump performed properly at a flow rate of 7200 gpm of 945 gas-cooled F sodium at 150-ft head. Results Hallam plant. (auth)
Date: June 30, 1960
Creator: Atz, R. W.
Partner: UNT Libraries Government Documents Department

Possible pion sources for radiotherapy

Description: From second meeting on fundamental and practical aspects of the application of fast neutrons in clinical radiotherapy; The Hague, Netherlands (3 Oct 1973). Recently great interest has been shown in pi-meson irradiation as a possible modality for cancer radiation therapy. In order for this short-lived particle to be more than an idle laboratory curiosity, it must be demonstrated that economical pion sources can be built, which satisfy the necessary flux requirements for therapy within reasonable space and cost limitations. Protons have a much higher probability for producing pions per unit target mass than do electrons, so if there were no other consideration it is clear that proton accelerators would be superior to electron accelerators as pion sources. Unfortunately, proton accelerators are considerably more difficult to build than electron accelerators, requiring more precise control, more rf power, and probably more length than their counterparts. At 500-MeV the advantage of protons over electrons for production is about a factor of 50, that is, for the same total yield of pions, an electron accelerator must have 50 times the beam power required of an equivalent proton machine. One possible way around this problem is to design a much more efficient magnetic channel to collect the pions and focus them on the patient being treated. Such a system has been designed that utilizes 60 parallel magnetic spectrometers to focus a total of 1/12 the total pions produced in the pion production target on the patient. This system requires a more sophisticated control system, but is certainly an indicator of a direction to go to reduce source cost. This approach also reduces the beam current requirements on a proton accelerator by a factor of 30 making a 30 microamp accelerator a possibility. A brief description of four accelerator systems that might be suitable for hospital ...
Date: January 1, 1973
Creator: Knapp, E.A.
Partner: UNT Libraries Government Documents Department

Uniform dose distribution with moving negative pion beams

Description: Dense ionization in the stopping region as negative pions come to rest in matter makes them attractive for treatment of cancer. Pions of the same energy have essentially the same range in matter which means that a monoenergetic beam will produce a Bragg peak region of maximum ionization as they come to rest. In cancer therapy, the entire treatment volume should be exposed, if possible, to the Bragg peak. A distribution of energy and adjustment of lateral dimensions could theoretically adjust the Bragg peak to fit into most any treatment volume but this inight be difficult in practice to accomplish. As an alternative, the beam can be tuned to produce a peak with known properties, and this peak can be moved in a controlled manner so as to scan the treatment volume. For a vertical beam, this method usually will require vertical oscillations of the beam as well as horizontal motion to cover the entire volume. Both of these motions can result in undesirable dose distributions. It is shown how to avoid or minimize the unwanted effects and it is also shown how velocity distributions can be determined for uniform effective dose throughout a treatment volume. (auth)
Date: July 1, 1973
Creator: Rodgers, E.
Partner: UNT Libraries Government Documents Department

Hadronic spectra in Au+Au reactions at 11.6 A{center_dot}GeV/c: Rapidity and m{sub t} distributions

Description: In central Au+Au collisions, the rapidity distribution of measured protons integrated over {ital m{sub t}} indicates almost complete stopping, hence high baryon density. For a given rapidity, low mt enhancement has been observed for {pi}{sup -} production over that of {pi}{sup +}. The Coulomb interaction with the co-moving medium has been invoked to explain the difference. The inverse slope parameters of the {ital m{sub t}} spectra for protons and deuterons increases from peripheral to central events, while the parameter for pions stays the same. This may indicate that a radial expansion follows the high density stage of the reaction.
Date: December 31, 1996
Creator: Chen, Ziping & Collaboration, E866
Partner: UNT Libraries Government Documents Department

Color transparency and pion valence quark distributions from di-jet events in Fermilab E791

Description: Diffractive, exclusive di-jet events produced by 500 GeV/c {pi}{sup {minus}} scattered off nuclei were used to measure their A-dependence, and to make the first direct measurement of the valence-quark momentum distribution in pions. Data on the latter are compared to two limiting predictions for the pion light-cone wave-function. The results show that the asymptotic wave-function of perturbative QCD describes the data well for Q{sup 2} of 10 GeV{sup 2} and above. The measured A-dependence is consistent with observation of point-like configurations in the pion and color-transparency calculations.
Date: October 10, 2000
Creator: Appel, Jeffrey A.
Partner: UNT Libraries Government Documents Department


Description: The recent papers of Jeon and Koch[l] and Asakawa, Heinz and Muller[2] propose that the event by event fluctuations of the ratio of the positively charged and negatively charged pions could provide a distinct signal for a QGP at RHIC/LHC due to differences in those from the QGP phase, and the Hadron Gas Phase. In this paper we point out that aside from the questionability of the many assumptions in the treatment used, even following their approach there are other effects not considered, e.g. color charge fluctuations which we show could significantly or completely wash out the proposed signal. Therefore lack of observation of these charge fluctuation signals cannot lead one to conclude that a QGP is not formed at RHIC. A general discussion of experimental requirements for observation of such signals (if they exist) and how to interpret them is included.
Date: August 1, 2001
Partner: UNT Libraries Government Documents Department

Review of charm lifetimes

Description: A review of the latest experimental results on charm particle lifetimes is presented. The most significant update is that the D{sub s}{sup +} lifetime is conclusively larger than the D{sup 0} lifetime and signifies that W-exchange/W-annihilation contributions are large. Using new high statistics data on D{sup +} {r{underscore}arrow} K{sup +}{pi}{sup +}{pi}{sup {minus}} together with the D{sub s}{sup +} lifetime and some assumptions, one can phenomenologically extract the strength of the W-exchange contribution in D{sup 0} decays and of W-annihilation in D{sub s}{sup +} decays. These are larger than or at the limit of theoretical expectations using QCD-based operator production expansion techniques.
Date: January 6, 2000
Creator: Cheung, H.W.K.
Partner: UNT Libraries Government Documents Department

Heating of nuclear matter and multifragmentation : antiprotons vs. pions.

Description: Heating of nuclear matter with 8 GeV/c {bar p} and {pi}{sup {minus}} beams has been investigated in an experiment conducted at BNL AGS accelerator. All charged particles from protons to Z {approx_equal} 16 were detected using the Indiana Silicon Sphere 4{pi} array. Significant enhancement of energy deposition in high multiplicity events is observed for antiprotons compared to other hadron beams. The experimental trends are qualitatively consistent with predictions from an intranuclear cascade code.
Date: May 3, 1999
Creator: Back, B.; Beaulieu, L.; Breuer, H.; Gushue, S.; Hsi, W.-C.; Korteling, R. G. et al.
Partner: UNT Libraries Government Documents Department

Direct flow in 10.8 GeV/nucleon Au+Au collisions measured in experiment E917 at the AGS.

Description: Analysis of directed flow observable for protons and pions from Au+Au collisions at 10.8 GeV/nucleon from experiment E917 at the AGS is presented. Using a Fourier series expansion, the first Fourier component, {nu}{sub 1},was extracted as a function of rapidity for mid-central collisions (17-24%). Clear evidence for positive directed flow is found in the proton data, and a weak, possibly negative directed flow signal is observed for {pi}{sup +} and {pi}{sup {minus}}.
Date: May 19, 1999
Creator: Back, B. B.; Betts, R. R.; Britt, H. C.; Chang, J.; Chang, W. C.; Gillitzer, A. et al.
Partner: UNT Libraries Government Documents Department

Observation of CP Violation in B0 to K+pi- and B0 to pi+pi-

Description: The authors report observations of CP violation in the decays B{sup 0} {yields} K{sup +}{pi}{sup -} and B{sup 0} {yields} {pi}{sup +}{pi}{sup -} in a sample of 383 million {Upsilon}(4S) {yields} B{bar B} events. They find 4372 {+-} 82 B{sup 0} {yields} K{sup +}{pi}{sup -} decays and measure the direct Cp-violating charge asymmetry {Alpha}{sub K{pi}} = -0.107 {+-} 0.018(stat){sub -0.004}{sup +0.007}(syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample they find 1139 {+-} 49 B{sup 0} {yields} {pi}{sup +}{pi}{sup -} decays and measure the CP-violating asymmetries S{sub {pi}{pi}} = -0.60 {+-} 0.11(stat) {+-} 0.03(syst) and C{sub {pi}{pi}} = -0.21 {+-} 0.09(stat) {+-} 0.02(syst). CP conservation in B{sup 0} {yields} {pi}{sup +}{pi}{sup -} (S{sub {pi}{pi}} = C{sub {pi}{pi}} = 0) is excluded at a confidence level 1-C.L. = 8 x 10{sup -8}, corresponding to 5.4 standard deviations.
Date: March 14, 2007
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Observation of Decays $B^0\to D_s^{(*)+}\pi^-$ and$B^0\to D_s^{(*)-}K^+$

Description: The authors report the observation of decays B{sup 0} {yields} D{sub s}{sup (*)+} {pi}{sup -} and B{sup 0} {yields} D{sub s}{sup (*)-} K{sup +} in a sample of 230 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} events recorded with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} storage ring. They measure the branching fractions {Beta}(B{sup 0} {yields} D{sub s}{sup +}{pi}{sup -}) = (1.3 {+-} 0.3(stat) {+-} 0.2(syst)) x 10{sup -5}, {Beta}(B{sup 0} {yields} D{sub s}{sup -}K{sup +}) = (2.5 {+-} 0.4(stat) {+-} 0.4(syst)) x 10{sup -5}, {Beta}(B{sup 0} {yields} D*{sub s}{sup +} {pi}{sup -}) = (2.8 {+-} 0.6(stat) {+-} 0.5 (syst)) x 10{sup -5}, and {Beta}(B{sup 0} {yields} D*{sub s}{sup -} K{sup +}) = (2.0 {+-} 0.5(stat) {+-} 0.4(syst)) x 10{sup -5}. The significance of the measurements to differ from zero are 5, 9, 6, and 5 standard deviations, respectively.
Date: April 19, 2006
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

Observation of $\Upsilon(4S) decays to$\pi^+pi^-\Upsilon(1S)$ and $\pi^+pi^-\Upsilon(1S)$

Description: The authors present the first measurement of {Upsilon}(4S) decays to {pi}{sup +}{pi}{sup -} {Upsilon}(1S) and {pi}{sup +}{pi}{sup -} {Upsilon}(2S) based on a sample of 230 x 10{sup 6} {Upsilon}(4S) mesons collected with the BABAR detector. They measure the product branching fractions {Beta}({Upsilon}(4S) {yields} {pi}{sup +}{pi}{sup -} {Upsilon}(1S)) x {Beta}({Upsilon}(1S) {yields} {mu}{sup +}{mu}{sup -}) = (2.23 {+-} 0.25{sub stat} {+-} 0.27{sub sys}) x 10{sup -6} and {Beta}({Upsilon}(4S) {yields} {pi}{sup +}{pi}{sup -}{Upsilon}(2S)) x {Beta}({Upsilon}(2S) {yields} {mu}{sup +}{mu}{sup -}) = (1.69 {+-} 0.26{sub stat} {+-} 0.20{sub sys}) x 10{sup -6}, from which they derive the partial widths {Lambda}({Upsilon}(4S) {yields} {pi}{sup +}{pi}{sup -} {Upsilon}(1S)) = (1.8 {+-} 0.4) keV and {Lambda}({Upsilon}(4S) {yields} {pi}{sup +}{pi}{sup -}{Upsilon}(2S)) = (2.7 {+-} 0.8) keV.
Date: April 19, 2006
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department

CP Violation in Tau to K* Decays

Description: A sample of {tau}{sup {+-}} {yields} K*{sup {+-}} decays with K*{sup {+-}} {yields} K{sub S}{sup 0}{pi}{sup {+-}} and K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -}, using 123.4 fb{sup -1} of data collected by the BaBar detector at the Stanford Linear Accelerator Center, is used to search for a direct CP violation effect in the charged Higgs sector. No evidence of CP violation is found and the imaginary part of the charged Higgs coupling, {l_brace}Im{r_brace}({Lambda}), in the Multi-Higgs-Doublet-Model is found to be at -0.284 &lt; {l_brace}Im{r_brace}({Lambda}) &lt; 0.200 at 90% Confidence Level. In addition the installation of the kk2f Monte Carlo generator into the BaBar software framework is described.
Date: March 10, 2006
Creator: Hodgkinson, Mark & U., /Manchester
Partner: UNT Libraries Government Documents Department

Measurement of \mathcal{B}(\tau^{-}\-->\bar{K^{0}}\pi^{-}\nu_{\tau}) Using the \babar Detector

Description: A preliminary measurement of the branching fraction {Beta}({tau}{sup -} {yields} K{sub S}{sup 0}{pi}{sup -}{nu}{sub {tau}}) is made using 384.6 fb{sup -1} of e{sup +}e{sup -} collision data provided by the PEP-II collider, operating primarily at {radical}s = 10.58 GeV, and recorded using the BABAR detector. From this they measure: {Beta}({tau}{sup -} {yields} {bar K}{sup 0}{pi}{sup -}{nu}{sub {tau}}) = (0.840 {+-} 0.004(stat) {+-} 0.023(syst))%. This result is the most precise measurement to date and is consistent with the world average.
Date: August 13, 2008
Creator: Wren, A
Partner: UNT Libraries Government Documents Department

Studies of the Strange Hadronic Tau Decay Tau- to K0(S) Pi- Nu-Tau Using the BaBar Detector

Description: A study of the decay {tau}{sup -} {yields} K{sub S}{sup 0}{pi}{sup -} {nu}{sub {tau}} (K{sub S}{sup 0} {yields} {pi}{sup +}{pi}{sup -}) using the BABAR detector is presented. Using 124.4 fb{sup -1} of data we measure {Beta}({tau}{sup -} {yields} {bar K}{sup 0}{pi}{sup -}{nu}{sub {tau}}) = (0.830 {+-} 0.005(stat) {+-} 0.042(syst))%, which is the world's most precise measurement to date of this branching ratio, and is consistent with the current world average. This preliminary result, unlike most of the {Beta}({tau}{sup -} {yields} {bar K}{sup 0}{pi}{sup -}{nu}{sub {tau}}) measurements already published, is systematics dominated and so the biggest future improvement to this number should come from reducing the systematic uncertainties in the analysis. A study of the K{pi} mass spectrum, from which the strange (K{pi}) spectral function can be measured, reveals excess contributions above the K*(892) tail at higher K{pi} mass. While in the past this has been thought to be due to K*(892) - K*(1410) interference, we find that the K*(1410), whose branching ratio to K{pi} is approximately 7%, seems insufficient to explain the excess mass observed in the data. Instead, we perform a fit using a K*(892) - K*(1680) interference model and find better agreement. The discrepancy that remains could be due to an s-wave contribution to the interference that is not parameterized in the model used, and/or detector smearing that is not accounted for in our fit. We also attempt to find an s-wave contribution to the K{pi} mass spectrum by searching for an sp-interference effect. While we find a hint that such an effect exists, we have neither the confidence in the statistics nor systematics in the higher K{pi} mass region to announce an observation. We conclude that it would be a worthwhile study to pursue.
Date: January 27, 2006
Creator: Lyon, Andrew J. & /SLAC, /Manchester U.
Partner: UNT Libraries Government Documents Department

Search for the Decay B^0 -> a^\pm_1 \rho^\mp

Description: The authors present a search for the rare B-meson decay B{sup 0} {yields} {alpha}{sub 1}{sup {+-}}{rho}{sup {-+}} with {alpha}{sub 1}{sup {+-}} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup {+-}}. We use (110 {+-} 1.2) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEp-II asymmetric-energy B Factory at SLAC. They obtain an upper limit of 30 x 10{sup -6} (90% C.L.) for the branching fraction product {Beta}(B{sup 0} {yields} {alpha}{sub 1}{sup {+-}}{rho}{sup {-+}}) {Beta}({alpha}{sub 1}{sup {+-}} {yields} {pi}{sup +}{pi}{sup -}{pi}{sup {+-}}), where they assume that the {alpha}{sub 1}{sup {+-}} decays exclusively to {rho}{sup 0}{pi}{sup {+-}}.
Date: May 10, 2006
Creator: Aubert, B.
Partner: UNT Libraries Government Documents Department