本文選題：粲偶素 + 新型強子結構�。� 參考：《山東大學》2017年博士論文

【摘要】：自從量子色動力學問世以來,對于微擾能區(qū)的物理量可以很完美地計算,但是對非微擾能區(qū)一向缺少精確計算及認識,對夸克受前相互作用束縛為強子時的規(guī)律更是缺少限制,由此人們一直在通過尋找新型強子結構以及高精度的測量來完善量子色動力學以對整個物質世界有更深地了解。北京正負電子對撞機上的BESⅢ探測器工作的粲夸克能區(qū)正是量子色動力學由微擾向非微擾的過渡區(qū)域,而且實驗上發(fā)現(xiàn)的可能擁有新型強子結構的奇特強子態(tài)也多數(shù)位于該區(qū)域,所以研究該區(qū)域中相應強子的產(chǎn)生與衰變機制以及尋找奇特強子態(tài)對研究量子色動力學有非常重要的意義。目前國際上多個粒子物理實驗已經(jīng)發(fā)現(xiàn)存在X(3872),Y(4140),Y(4260),Y(2175)以及Ds0*(2317)等與常規(guī)強子性質截然不同的共振態(tài),這些態(tài)均以不同尋常的衰變模式出現(xiàn)在不同尋常的位置上。人們普遍認為這些態(tài)極有可能擁有新型強子結構,并提出多種理論模型試圖去解釋它們的存在,但是實驗結果的匱乏使得人們離理解這些態(tài)的內部結構還有很遠的距離。本文致力于利用BESⅢ上質心系能量在3.7 GeV之上的正負電子對撞數(shù)據(jù)尋找并研究上述態(tài),具體為尋找它們的新產(chǎn)生和衰變模式,以及它們之間的關聯(lián),從而為全面理解這些態(tài)提供關鍵的信息。利用BESⅢ探測器在質心系能量(?)=4.26 GeV附近的數(shù)據(jù),我們首次通過e+e-→ γπ+π-(ρ)J/φ過程觀測到著名的奇特強子態(tài)候選者X(3872),其信號統(tǒng)計顯著性超過10σ,測得質量為3872.6 ± 0.5 ± 0.2 MeV/c2,其中后兩項分別為統(tǒng)計和系統(tǒng)誤差。測量得到的各個能量點下的截面分布顯示X(3872)很可能來自于另一奇特強子態(tài)候選者Y(4260)的輻射躍遷,并且分支比與Y(4260)→ π+π-J/φ相當。該結果首次發(fā)現(xiàn)X(3872)與Y(4260)態(tài)相關聯(lián),表明其具有類似的本質,除目前僅知的B介子衰變以及強子對撞外,此過程發(fā)現(xiàn)新的X(3872)產(chǎn)生機制,并且為Y(4260)除了π+π-J/φ之外新的衰變模式,為理解這些態(tài)提供強有力的信息。在BESⅢ上繼發(fā)現(xiàn)X(3872)之后,我們利用相同的數(shù)據(jù)通過e+e-→γφJ/φ過程對另一奇特強子態(tài)候選者Y(4140)進行了尋找因為Y(4140)與X(3872)可能為同一類型強子態(tài),其中分別用K+K-,KS0欠L0和π+π-π0道重建φ然后合并分析,所有數(shù)據(jù)中均沒有觀測到明顯的信號,我們給出相應過程在質心系能量為4.23,4.26和4.36 GeV處的截面在90%置信度下的上限分別為0.35,0.38和0.33 pb。結合之前所測量的γX(3872)產(chǎn)生截面,以及在分子態(tài)模型下計算的Y(4140)→φJ/φ分寬度可以得到在4.23和4.26 GeV下兩個過程的截面比σ(e+e-→-γY(4140))/(e+e-→ γX(3872))處于0.1的量級或者更小。在奇異夸克偶素能區(qū)的奇特強子態(tài)候選者Y(2175),有與Y(4260)類似的性質,我們利用BESⅢ采集的質心系能量在3.7 GeV之上的數(shù)據(jù)首次觀測到e+e-→ ηY(2175)過程,聯(lián)合所有數(shù)據(jù)得到的統(tǒng)計顯著性超過10σ,這是實驗觀測的Y(2175)新的產(chǎn)生機制。測得Y(2175)質量為2135±8±9 MeV/c2,寬度為104 ±24 土 12 MeV,這里兩項誤差分別為統(tǒng)計和系統(tǒng)誤差。各個能量點上的截面中,沒有發(fā)現(xiàn)明顯的粲偶素貢獻,與預期的矢量贗標量過程的分布相吻合。同時利用質心系能量為3.686 GeV包含(447.9 ± 2.9)× 106個φ(3686)事例的數(shù)據(jù)尋找φ(3686)→ηY(2175)過程,并沒有發(fā)現(xiàn)顯著信號,考慮J/φ和φ(3686)衰變的相空間差異之后的分支比比例B*(φ(3686)→ηY(2175))/B*(J/φ → η(2175))=(0.23 ± 0.29 ± 0.13)%,與 12%規(guī)則相比有非常大的壓低,這也是新的不符合該規(guī)則的矢量贗標量過程。同時我們用相同的數(shù)據(jù)尋找e+e-→ η'Y(2175)過程,沒有發(fā)現(xiàn)明顯信號,聯(lián)合所有數(shù)據(jù)得到的截面之比σ(e+e-→ η'Y(2175))/σ(e+e-→ ηY(2175))在90%置信度下的上限為0.43。除夸克偶素能區(qū)外,在粲介子能區(qū)也發(fā)現(xiàn)有常規(guī)夸克模型很難解釋的態(tài),其中人們認知最少也是最感興趣的為Ds0*(2317)±。我們利用BESⅢ在質心系能量為4.6 GeV采集的566.93 pb-1數(shù)據(jù)首次通過Ds*(?)的反沖質量信息觀測到 Ds0*(2317)±信號,測得Ds0*(2317)質量為(2318.3± 1.2±1.2)MeV/c2,統(tǒng)計顯著性為5.8σ,并利用Ds*(?)的反沖側信息通過部分重建Ds0*(2317)±的方法首次測量了Ds0*(2317)衰變的絕對分支比B(Ds*0(2317)±→ π0Ds±)為1.00-0.14±0.14,這里兩項誤差分別為統(tǒng)計和系統(tǒng)誤差。該結果表明Ds0*(2317)±的衰變中π0Ds±占絕對主導部分,與常規(guī)粲介子cs模型下的預期有差異,卻與分子態(tài)模型下的計算相吻合。在粲介子對閾值以上,預期所有矢量粲偶素或類粲偶素傾向于衰變到粲介子對末態(tài),所以精確測量這些粲介子對的產(chǎn)生截面對理解這些(類)粲偶素有非常重要的意義。我們利用BESⅢ所采集的從Ds+Ds-閾值直到質心系能量為4.6 GeV處的超過100個能量點下的數(shù)據(jù)精確測量了 e+e-→D+Ds-過程的玻恩截面,我們分別重建一個Ds+和-并測量相應截面,之后再合并兩組結果。從截面隨質心系能量的分布中在4.23 GeV即Ds*+Ds*-質量閾值附近發(fā)現(xiàn)Ds+Ds-過程有明顯的增強效應,該處的奇特結構也可能來自于Y(4260)與周圍其它粲偶素之間的干涉效應。
[Abstract]:Since the advent of quantum chrodonic dynamics, the physical quantity of the perturbation energy region can be perfectly calculated, but the non perturbation energy region has always been lack of accurate calculation and understanding. The law of the quark's pre interaction as a hadron is lack of restriction, so people have been through searching for new hadronic structures and high precision measurements. To improve the quantum color dynamics to understand the whole material world, the charm quark area of the BES III detector on the Beijing positive and negative electron collider is the transition region of the quantum chromatic dynamics from the perturbation to the non perturbative, and the strange hadron states that may have the new hadron structure found in the experiment are mostly located in the region. So it is of great significance to study the generation and decay mechanism of the corresponding hadron in the region and to find the odd hadron states for the study of quantum chromo dynamics. At present, many particle physics experiments in the world have found the existence of X (3872), Y (4140), Y (4260), Y (2175), and Ds0* (2317), which are completely different from the conventional hadron properties. It is generally believed that these states are highly likely to have a new hadron structure, and a variety of theoretical models are proposed to explain their existence, but the lack of experimental results makes people far away from understanding the internal structures of these states. To find and study the above states by using the positive and negative electron collisions data of the BES III superior mass on 3.7 GeV, it is specific to find their new generation and decay patterns, and the correlation between them, so as to provide the key information for the comprehensive understanding of these states. The data near the =4.26 GeV of the mass heart (?) =4.26 GeV are used. We first observed the famous strange hadron candidate X (3872) through the process of e+e- - gamma - PI + - (rho) - (rho) - (rho) J/ phi. The statistical significance of the signal was more than 10 sigma, and the measured mass was 3872.6 + 0.5 + 0.2 MeV/c2, and the latter two items were statistical and systematic error respectively. The distribution of X (3872) at each of the measured points showed that X (3872) was likely to come from In another strange hadron candidate Y (4260), the radiative transition, and the branch ratio is equivalent to Y (4260) - PI + PI -J/. The result is first found that X (3872) is associated with Y (4260) state, indicating that it has a similar nature, except for the only known B meson decay and hadron colliding, this process finds a new X (3872) generation mechanism, and is Y (4260) except for Y (4260)). The new decay mode outside PI + PI -J/ Phi provides strong information for understanding these states. After the discovery of X (3872) on BES III, we use the same data to search for another strange hadron candidate Y (4140) through the e+e- to gamma J/ Phi process, because Y (4140) and X (3872) may be the same type of hadronic state, of which K+K-, respectively. KS0 is under L0 and PI + pi - pi 0 channel reconstruction phi and then combined analysis. No obvious signals are observed in all data. We give the cross section at the upper limit of the 90% confidence level at the 90% confidence level at the 90% confidence level in the mass of the mass of the mass, respectively, to produce the cross-section of the measured gamma X (3872) before the combination of the 0.35,0.38 and 0.33 pb., respectively, and in the molecular mode. The width of Y (4140) - J/ Phi can be calculated in the two processes of 4.23 and 4.26 GeV (e+e- to - gamma Y (4140)) / (e+e- to gamma X (3872)) at the order of 0.1 or smaller. The strange hadron candidate in the singular quarkeven energy region Y (2175) has the properties similar to Y (4260). We use the centroid system collected by BES III For the first time, the data above 3.7 GeV observed the e+e- > Y (2175) process. The statistical significance of the combined data is more than 10 sigma. This is the new generation mechanism of the experimental observation Y (2175). The mass of Y (2175) is 2135 + 8 + 9 MeV/c2, and the width is 104 + 24 soil 12 MeV, and the two errors are respectively statistical and systematic error. Each energy is respectively energy. No obvious charm contribution is found in the cross section of the point, which is consistent with the expected distribution of the pseudo scalar process. At the same time, the data of the centroid system energy is 3.686 GeV including (447.9 + 2.9) x 106 (3686) cases to find the (3686) - ETA Y (2175) process, and no significant signals are found, considering the phase space of the decay of J/ phi and (3686). The branch ratio after the difference ratio B* (3686) - ETA Y (2175)) /B* (J/ [1] (2175)) = (0.23 + 0.29 + 0.13)%, compared with the 12% rule, has a very large reduction. This is a new vector pseudo scalar process that does not conform to the rule. At the same time, we use the same data to find the e+e- to'Y (2175) process, no obvious signals are found, United ownership is found. The ratio of the ratio of the cross section of the data (e+e- to ETA'Y (2175)) / (e+e- to ETA Y (2175)) at 90% confidence level is 0.43. except quark dienergy region, and the normal quark model is also difficult to explain in the charmed meson region. In which people have the least cognition and the most interesting is Ds0* (2317). We use BES III in the mass of the heart system to be 4. The 566.93 PB-1 data collected by.6 GeV observed the Ds0* (2317) + signal for the first time through the Ds* (?) recoil quality information, and measured the Ds0* (2317) mass of (2318.3 + 1.2 + 1.2) MeV/c2, and the statistical significance was 5.8 sigma, and the absolute branch ratio of Ds0* (2317) decay was first measured by using the Ds* (?) backflash information to measure the absolute branching ratio of Ds0* (2317) decay for the first time (D). S*0 (2317) + + 0Ds +) is 1.00-0.14 + 0.14, and the two errors here are statistical and systematic errors, respectively. The results show that the absolute dominant part of the Ds0* (2317) + decay is in the absolute dominant part, which is different from the conventional charm meson CS model, but is consistent with the calculation under the molecular model. All vector charms are expected above the charmed meson to the threshold value. It is very important to accurately measure the production cross sections of these charmed meson pairs to understand these (class) charm pairs. We use the data collected by BES III to measure e+e- accurately from the data of the Ds+Ds- threshold at 4.6 GeV at the energy of the centroid system until the energy of the centroid system is at 4.6. The Born section of the D+Ds- process, we reconstruct a Ds+ and - and measure the corresponding section, and then combine the two sets of results. It is found that the Ds+Ds- process has obvious enhancement effect near the distribution of mass heart system energy in the vicinity of 4.23 GeV, that is, the Ds*+Ds*- mass threshold, and the peculiar structure of the branch may also come from Y (4260) and the surrounding other charms. The interference effect between even elements.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O572.243
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本文編號：2065622