The MARK III Collaboration
The MARK III Collaboration
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发表时间：
1986
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通讯作者：
A. Odian;W. Stockhausen;F. Villa;S. Wasserbaech;N. Wermes;D. Wisinski
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作者：
A. Odian;W. Stockhausen;F. Villa;S. Wasserbaech;N. Wermes;D. Wisinski
研究了J/+ +77 rr +7 rr和J/$J +7 K +K-（MK+K<2.0GeV/c ~ 2）衰变。给出了BR（11，+ 7 f（1270））的测量结果。BR（f（1270）+ T+T-），BR（+ +~（1720））。BR（B（1720）+ m+F）、BR（$ + 7 f '（1525））、BR（f'（1525）+ W-K-）和BR（T，！J + 70））-BR（B（1720）+ K+K-）。在z + z通道中观察到更高质量的结构。0（1720）的自旋是以高置信度建立的。确定了f（1270），f '（1525）和δ（1720）的偏振结构。根据合同DE-AC 02 - 76 ER 01195、DE-AC 03 - 81 ER 40050、DE-AM 03 - 76 SF 0034，部分由能源部支持的工作提交给物理评论D。1. J/v）到77 r +7和yK+ K的辐射衰变本文讨论了J/t）到所有运动学可达不变质量的m+ z系统和2.0GeV/c ~ 2以下的K+ K系统的辐射衰变。量子色动力学（QCD）承认两个或多个胶子的无色束缚态的可能性，这些胶子被称为胶球。J/T）的辐射衰变已经被证实是胶球搜索的有希望的模式。根据微扰QCD，J/t，B与通过7 gg衰变的J/t，b的比值为r（J/+ -）w）36 2a2.2cY，2F（J/11，+ 999）= Ye，l++** a8 [7 r1]对于CX~ = 0.2，这导致分支分数BR（J/+ +72 g）510%.因此，预期所有J/t）衰变的相当大部分通过辐射衰变图进行。由双胶子系统产生的强子末态具有C = +和I = 0。据计算141，Jpc = O++，O-+，2++主导J/$ +7 X最终状态，并且Jpc = l-和l-+被抑制。最容易接近的末态是那些包含两个或三个伪标量的状态。两个伪标量可以联合收割机产生Jpc = 0++，2 ++态，而三个伪标量可以形成Jpc = O-+态.在2++通道中，f（1270）在zz模式中非常突出。这种最终态的产生特性（即不同偏振态的总体）已经通过MARK II和水晶球实验测量。15 p61 f '（1525）h可以通过MARK II实验[8]在K+ K最终态中看到。8（1720）h分别在水晶球和马克II实验中以qq和K+ K衰变模式观测到，他们只将其衰变限制在zz。[s] l. lgl S ~*（975）是一个I = 0，O ~（++）态，在辐射衰变中明显不存在。2. Mark III探测器Mark III探测器是一个通用的磁谱仪，针对SPR 10能量区域进行了优化。设计目标是一个能够完全重建排他性最终状态的检测器。在SPV，带电和中性的平均多重性各约为4。带电粒子和中性粒子的动量谱峰值分别为500 MeV/c和250 MeV/c。该检测器的突出特点是：1。铍射束管具有低质量触发室，以最小化多次散射。2.对47 r的带电径迹立体角覆盖率为85%，对4~ 2 r的中性径迹覆盖率为95%。3.使用分辨率为190 ps的飞行时间系统（TOF）对带电径迹进行了良好的粒子识别。4.一个精细分段的簇射计数器，对低能光子有很好的探测效率，电子-强子分离良好，能量分辨率AE/E = 17%/a。5.在螺线管线圈外的两层钢和μ子计数器用于μ子-强子分离，覆盖了47 r的65%。检测器设计在图1A和1B中以轴向和横向视图示出。2.1分别为2.2。3. J/~/J + yrr+ rr的77 r +7 r末态事件选择必须在簇射计数器中观测到辐射光子。要求事件具有少于5个孤立光子，其中“孤立”意味着cos B，，< 0.95。由于带电强子在簇射计数器中相互作用的产物有时被计为光子，所以允许有一个以上的光子。
The decays J/+ + 77rr+7rrand J/$J + 7K+K-, MK+K< 2.0 GeV/c2, have been studied. Measurements are presented for BR(11, + 7 f (1270)) . BR( f (1270) + T+T-), BR(+ + ~~(1720)) . BR(B(1720) + m+F), BR($ + 7 f’(1525)) BR(f’(1525) + W-K-), and BR(T,!J + 70)) -BR(B(1720) + K+K-). A higher mass structure is observed in the z + z channel. The spin of the 0(1720) is established with high confidence. The polarization structure of the f (1270), f’(1525), and 8(1720) have been determined. Submitted to Physical Review D t Work supported in part by the Department of Energy, under contracts DE-ACOS76SF00515, DE-AC02-76ER01195, DE-AC03-81ER40050, DE-AM03-76SF0034, and by the National Science Foundation. 1. Radiative Decays of the J/v) into 77r+7rand yK+KThis paper deals with J/t) radiative decays to m+zsystems of all kinematitally accessible invariant masses and to K+Ksystems below 2.0 GeV/c2.[‘l KK masses above 2.0 GeV/c2 have been treated separately.12] Quantum Chromodynamics (QCD) admits the possibility of colorless bound states of two or more gluons which have been named glueballs. Radiative decays of the J/T) h ave been suggested131 as promising modes for glueball searches. The ratio of J/t,b decays via 7gg to those via ggg, according to perturbative QCD, is r(J/+ --) w) 36 2 a 2.2cY, 2 F(J/11, + 999) = Ye,l++ *** a8 [ 7r 1 For CX~ = 0.2, this leads to a branching fraction BR(J/+ + 72g) 5 10% . Thus, a substantial fraction of all J/t) decays are expected to proceed through the radiative decay diagram. Hadronic final states produced from the two gluon system have C = + and I = 0. It was calculated141 that Jpc = O++,O-+, 2++ dominate the J/$ + 7X final state and that Jpc = l-and l-+ are suppressed. The final states most accessible are those containing two or three pseudoscalars. Two pseudoscalars can combine to produce states with Jpc = 0++,2++, while three pseudoscalars can form Jpc = O-+ states. In the 2++ channel, the f (1270) appears very prominently in the zz mode. The production characteristics (i.e. the population of the different polarization states) of this final state have been measured by the MARK II and Crystal Ball experiments.15p61 The f’(1525) h as b een seen by the MARK II experiment[8] in the K+Kfinal state. The 8(1720) h as been observed in the qq and K+Kdecay modes by the Crystal Ball and Mark II experiments, respectively; they have only set limits on its decay to zz.[s~‘l. The 8(1720) has been suggested as a glueball candidate.lgl The S* (975), an I = 0, O++ state, is notably absent from radiative J/T) decays. 2. The Mark III Detector The Mark III detector[lol is’a general purpose magnetic spectrometer, optimized for the SPEAR energy region. The design goal was a detector capable of complete reconstruction of exclusive final states. At SPEAR, the mean charged and neutral multiplicities are each about four. The momentum spectra for charged and neutral particles peaks at 500 MeV/c and 250 MeV/c, respectively. The salient features of the detector are: 1. A beryllium beam pipe with a low mass trigger chamber to minimize multiple scattering. 2. A charged-track solid-angle coverage of 85% of 47r, and a neutral track coverage of 95% of 4~. 3. Good particle identification for the charged tracks using a time of flight system (TOF) with a resolution of 190 ps. 4. A finely segmented shower counter with good detection efficiency for low energy photons, good electron-hadron separation, and an energy resolution of AE/E = 17%/a. 5. Two layers of steel and muon counters outside the solenoidal coil for muon-hadron separation covering 65% of 47r. The detector design is shown in axial and transverse views in Figs. 2.1 and 2.2, respectively. 3. The 77r+7rFinal State Event Selection for J/~/J + yrr+rrThe radiative photon must be observed in the shower counter. Events are required to have fewer than 5 isolated photons, where ‘isolated’ means cos B,, < 0.95. More than one photon is allowed since the products of charged hadrons interacting in the shower counter are sometimes counted as photons.