118715122
Physics from Tristan
The TRISTAN e + e − storage ring has delivered a total of about 60 pb−1 to each of the three general purpose solenoidal detectors: AMY, TOPAZ and VENUS. The center-of-mass energy range, between 50 and 64 GeV, is where interference effects between the virtual photon and Z0 mediators of the annihilation process are largest. Experiments at TRISTAN study the electroweak interactions, QCD, and search for new phenomena. Among the reported results are: measurements of R; the observation of forward-backward charge asymmetries for e+e− → lepton pairs, \(e^ + e^ - \to b\bar b\), and \(e^ + e^ - \to q\bar q\); limits on lepton compositeness; determinations of \(\Lambda _{\overline {MS} }\); measurements of various multihadron event properties; evidence for differences between quark and gluon jets; the demonstration of the running of αs and the existence of the triple-gluon coupling; and searches for a variety of new particles. This report describes a few selected results from the AMY experiment.
119304627
The evolution of FTK, a real-time tracker for hadron collider experiments
We describe the architecture evolution of the highly-parallel dedicated processor FTK, which is driven by the simulation of LHC events at high luminosity (1034 cm-2 s-1). FTK is able to provide precise on-line track reconstruction for future hadronic collider experiments. The processor, organized in a two-tiered pipelined architecture, execute very fast algorithms based on the use of a large bank of pre-stored patterns of trajectory points (first tier) in combination with full resolution track fitting to refine pattern recognition and to determine off-line quality track parameters. We describe here how the high luminosity simulation results have produced a new organization of the hardware inside the FTK processor core.
73541758
PLS RF system operation during the commissioning
The storage ring of the Pohang Light Source (PLS) is designed to store 100s mA of 2 GeV electrons injected from the full energy linear accelerator. To compensate for the synchrotron radiation loss three RF cavities were installed in one of the straight sections powered by three 60 kW-TV transmitters independently. Phase and amplitude are controlled by the separate low level systems. During the commissioning, since the beam lifetime is limited by the vacuum pressure, various accelerating voltages were set to investigate the system characteristics. Even one cavity is enough to store 100 mA of beam, whereas the vacuum-limited lifetime is few minutes at 1 mTorr. The cavity HOM-induced multi-bunch instabilities were observed at certain condition and cured to some extent by shifting phase and water temperature. General description of RF system performance and trouble-shoots during the commissioning are presented.
120290177
Covariant Harmonic Oscillators and Excited Baryon Decays
We use the covariant harmonic oscillator wave functions to study the decay matrix elements of the excited baryonic resonances. It is pointed out that the harmonic oscillator wave function is suitable for the description of relativistic extended particles. We use the probability concept of the covariant harmonic oscillator wave functions and the covariant Dirac spinors to calculate the Jrr decays of the F,. (1690), D,. (1690) and D,. (1520) resonances. Our numerical results are in good agreement with the measurable ratios in these decay processes.
56009963
Single bunch collective effects in PLS storage ring
The single bunch collective effects such as the bunch lengthening due to the potential well distortion and the microwave instability which also increases the energy spread, the transverse head-tail instability, and the transverse strong head-tail instability are investigated in the Pohang Light Source storage ring. The threshold current and the Chao-Gareyte scaling factor of the bunch lengthening, the longitudinal broadband impedance, and the transverse impedance have been measured and compared with the ZAP code results.
16045203
Internal space‐time symmetries of massive and massless particles
A unified description is given for internal space‐time symmetries for massive and massless particles. It is noted that the little groups governing the internal symmetries of massive and massless particles are locally isomorphic to the three‐dimensional rotation group or O(3) and the two‐dimensional rotation group or E(2), respectively. It is noted also that the E(2) group can be obtained from a large‐radius/flat‐surface approximation of O(3). This procedure is then shown to be directly applicable to that of obtaining the E(2)‐like little group for massless particles from the O(3)‐like little group for massive particles in the infinite‐momentum/zero‐mass limit.
117351482
Bubble chamber study of (10÷100) GeV cosmic-ray muons at all zenith angles
SummaryCosmic-ray muons have been studied by analysis of tracks recorded in a large high-field heavy-liquid bubble chamber. From a sample of 50 000 pictures approximately 2 000 muons with energies above 10 GeV were examined for energy and zenith-angle distributions over the complete range from 0° to 90°. In the vertical direction the integral spectrum up to energies exceeding 100 GeV is consistent with depth intensity data and somewhat higher than observed in unshielded vertical magnetic spectrometers. At other zenith angles we find the expected variations, which approach a cos2ϑ attenuation for muons in the 10 GeV region, and tend towards a secϑ enhancement for muon energies above 100 GeV.RiassuntoSi sono studiati i muoni dei raggi cosmici analizzando le tracce fotografate in una grande camera a bolle a liquido pesante con forte campo magnetico. Da un campione di 50 000 fotogrammi si sono esaminati approssimativamente 2 000 muoni con energie superiori a 10 GeV per le distribuzioni di energia e dell’angolo zenitale nell’intero intervallo da 0° a 90°. Nella direzione verticale lo spettro integrale fino ad energie superiori ai 100 GeV è coerente con i dati sull’intensità in profondità ed è leggermente superiore a quello osservato in spettrometri magnetici verticali non schermati. Ad altri angoli zenitali si trovano le variazioni previste, che approssimano una attenuazione del tipo cos2ϑ per muoni nella regione di 10 GeV, e tendono verso un incremento del tipo secϑ per energie dei muoni al di sopra dei 100 GeV.РеэюмеБыли исследованы мюоны в космических лучах посредством аналиэа треков, эарегистрированных в пуэырьковой камере с тяжелой жидкостью, помешенной в сильном поле. Иэ выборки 50000 снимков были исследованы приблиэительно 2000 мюонов с знергиями около 10 ГзВ для получения знергетических распределений и распределений по эенитному углу во всей области углов от 0° до 90°. В вертикальном направлении интегральный спектр вплоть до знергий, превыщаюших 100 ГзВ, согласуется с данными глубинной интенсивности и до некоторой степени выще, чем наблюденный в незкранированных вертикальных магнитных спектрометрах. При других эенитных углах мы обнаружили предполагаемые иэменения, которые почти похожи на ослабление соs2 ϑ для мюонов в области 10 ГзВ и стремятся к увеличению вес ϑ для знергий мюонов выще 100 ГзВ.