發(fā)布時間：2018-03-19 17:31

  本文選題：ATLAS探測器　切入點：重離子碰撞　出處：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：重味夸克偶素(簡稱夸克偶素)指有正反粲夸克或底夸克對組成的介子。本論文主要基于ATLAS探測器收集的實驗數(shù)據(jù)通過雙繆子衰變道對五個S波夸克偶素(J/Ψ、Ψ(2S)和γ(nS)(n= 1,2,3))在核子-核子對質(zhì)心系能量為5.02 TeV的質(zhì)子-質(zhì)子對撞、質(zhì)子-鉛核對撞和鉛核-鉛核對撞中的產(chǎn)生過程進行了重建,其中粲夸克偶素根據(jù)產(chǎn)生來源的不同區(qū)分為:直接由部分子相互作用產(chǎn)生的瞬發(fā)粲夸克偶素和由6強子衰變而來的非瞬發(fā)粲夸克偶素。本論文對于5.02 TeV的質(zhì)子-質(zhì)子碰撞中對于不同橫動量和快度區(qū)間的S波夸克偶素產(chǎn)生截面,以及粲夸克偶素和底夸克偶素激發(fā)態(tài)相對于基態(tài)的產(chǎn)額比進行了測量。由于探測器性能約束,本論文僅給出了橫動量區(qū)間為8pT40 GeV和快度區(qū)間為|y|2.0的粲夸克偶素的測量結(jié)果。其中瞬發(fā)和非瞬發(fā)粲夸克偶素的截面分別與對應(yīng)的理論模型預(yù)言相符合,同時粲夸克偶素激發(fā)態(tài)到基態(tài)產(chǎn)額比和已發(fā)表的ATLAS測量結(jié)果符合較好。底夸克偶素的測量是基于橫動量區(qū)間pT40 GeV和快度區(qū)間|y|2.0。相對于粲夸克偶素,底夸克偶素具有更大的不變質(zhì)量和較小的對末態(tài)繆子的Lorentz推動,因而可以將橫動量測量量區(qū)間擴展到0 GeV。底夸克偶素的激發(fā)態(tài)到基態(tài)產(chǎn)額比在5.02 TeV質(zhì)子-質(zhì)子碰撞中的測量結(jié)果和7 TeV的結(jié)果類似。粲夸克偶素核底夸克偶素的測量結(jié)果都說明在質(zhì)子-質(zhì)子碰撞中,激發(fā)態(tài)到基態(tài)產(chǎn)額比相對于碰撞質(zhì)心系能量的依賴較弱。夸克偶素產(chǎn)生在重離子碰撞中的核修正因子和雙重產(chǎn)額比,可以通過對比其在重離子碰撞中和在質(zhì)子-質(zhì)子碰撞的產(chǎn)額得到。本論文中對于質(zhì)子-鉛核碰撞的研究表明,在ATLAS探測器測量的運動學(xué)區(qū)間內(nèi)沒有發(fā)現(xiàn)核效應(yīng)對J/Ψ的產(chǎn)額有顯著影響,而低橫動量的γ(1S)在質(zhì)子-鉛核對撞的產(chǎn)額表現(xiàn)出被壓制。也就是說質(zhì)子-鉛核碰撞對高橫動量的夸克偶素表現(xiàn)為質(zhì)子-質(zhì)子碰撞的簡單疊加,而同時也存在對于影響低橫動量的夸克偶素產(chǎn)額的機制。質(zhì)子-鉛核對撞中夸克偶素雙重產(chǎn)額比,即質(zhì)子-鉛核中的激發(fā)態(tài)到基態(tài)產(chǎn)額比與質(zhì)子-質(zhì)子中的激發(fā)態(tài)到基態(tài)產(chǎn)額比之比,可以給出末態(tài)相互作用效應(yīng)對于基態(tài)和激發(fā)態(tài)的影響的比較。粲夸克偶素核底夸克偶素雙重產(chǎn)額比的測量結(jié)果都預(yù)示著質(zhì)子-鉛核碰撞中存在著依賴于夸克偶素大小和核介質(zhì)大小的末態(tài)相互作用。受限于實驗精度,該結(jié)果僅有一個標準差的顯著度。在質(zhì)子-鉛核碰撞測量結(jié)果的基礎(chǔ)上,本論文也對鉛核-鉛核碰撞中的粲夸克偶素產(chǎn)生進行了測量。測量的運動學(xué)區(qū)間和質(zhì)子-質(zhì)子以及質(zhì)子-銀核碰撞保持一致。測量結(jié)果表明瞬時和非瞬時J/Ψ的產(chǎn)生在鉛核-鉛核碰撞中被顯著壓低。結(jié)合質(zhì)子-鉛核碰撞中的測量結(jié)果,這種壓低應(yīng)該全部貢獻于高溫高密夸克膠子等離子中所獨有的"熱效應(yīng)"。也就說ATLAS探測器提供了一個干凈的、基于粲夸克偶素來專門研究熱效應(yīng)的窗口。瞬時粲夸克偶素關(guān)于碰撞中心度的依賴在定性上和Debye色屏蔽效應(yīng)的預(yù)言一致,但定量上還有待和模型預(yù)言進行仔細比對。而非瞬時粲夸克偶素產(chǎn)額的壓低對研究b強子在夸克膠子等離子體的能量損失提供了一個間接的工具。鉛核-鉛核碰撞中的雙重產(chǎn)額比的結(jié)果表明Ψ(2S)的產(chǎn)額相較于J/Ψ經(jīng)歷了程度更強的壓低。這可能是Debye色屏蔽效應(yīng)存在的另外一個信號,但是我們也不能排除這種更強的壓制由冷核效應(yīng)貢獻的可能性。
[Abstract]:Heavy quarkonium (the quarkonium) refers to has a charm quark or bottom quark meson pairs in the thesis. The experimental data collected by ATLAS detector based on double muon decay channel of five S wave quarkonium (J/ psi, psi (2S) and gamma (n= (nS) 1,2,3)) in the nuclear energy - nuclear confrontation with sub - 5.02 TeV proton proton collisions, proton nuclear generating process of lead and lead - lead at the nuclear nuclear collisions were reconstructed, the charmonium according to different sources of distinction: direct by Parton interactions, instant charm positronium and by 6 hadronic decay from non prompt charmonium collision. This paper for 5.02 TeV proton proton in S wave quarkonium for different transverse momentum and rapidity region in cross section, and charmonium and bottomium excited state relative to the ground state yield ratio in the measurement. Because the detector performance constraints, this paper only gives the transverse momentum range of 8pT40 GeV and speed range for the measurement results of charmonium |y|2.0. The section of instant and non instant charmonium respectively with the corresponding theoretical model predictions are consistent with the charmonium excited state to ATLAS measurement the ground state yield ratio and published in good agreement with the measurements. The bottom quarkonium is transverse momentum and rapidity interval interval pT40 GeV |y|2.0. relative to the charmonium based bottomium has a constant quality and less more of the final muon Lorentz drive, which can measure the transverse momentum the amount of range extended to 0 GeV. bottomium excited state to the ground state yield ratio measurement results in proton proton collision of 5.02 TeV and 7 TeV in the similar results. The charmonium nuclear bottomium measurement results are described in the proton Proton collisions in the excited state to the ground state yield ratio relative to the weak dependence of mass system collision energy. Quarkonium nuclear modification factor in heavy ion collisions and double yield ratio, can yield by contrast in the heavy ion collisions in proton proton collisions. Research on proton nuclear lead this paper shows that the collision, in the Sports School District ATLAS detector measuring room not found significantly affected the yield of J/ is the nuclear effect, while the low transverse momentum gamma (1S) suppressed by proton nuclear collisions lead yield show. That is to say of quarkonium proton nuclear collisions lead to high transverse momentum in the performance of the simple superposition of proton proton collisions, but also has influence on low transverse momentum quarkonium production mechanism. Proton nuclear collisions lead quarkonium double yield ratio, namely the ratio of the yield of excited state to the ground state proton nuclear in the lead With the proton proton in the excited state to the ground state yield ratio, can be given the final state interaction effect on the ground and excited state. The charmonium nuclear bottomium double yield ratio measurement results indicate that there exists interaction depends on the size of the quark positronium and nuclear medium size of final proton nucleus collisions. Lead is limited by the accuracy of the experiment, the results of only one standard deviation of significant degree. Based on measurement results of proton nuclear collisions on the lead, the lead - lead nuclear charm even in nuclear collisions generate were measured. The measurement of sports school and the proton proton proton collision and silver core consistency. The measurement results show that the instantaneous and non instantaneous J/ psi production was significantly lower in the lead - lead nuclear nuclear collisions. Combined with the measurement results of proton - lead in nuclear collisions, this should all contribute to the high temperature down High density quark gluon plasma in the unique "thermal effect". It said ATLAS detector provides a clean window, I have devoted to the study of the charm quark. Based on the thermal effect on instantaneous charmonium on collision centrality in qualitative and Debye color screening effect is consistent, but quantitative also need to be carefully compared. And the model predicted and non instantaneous charmonium yield down to study B hadron provides an indirect tool of energy loss in the quark gluon plasma. Nuclear lead - lead in nuclear collisions double yield ratio (2S) results show that only the yield compared to in J/ only experienced more depression. This may be another sign of Debye color screening effect, but we can not rule out the possibility of suppressing the stronger by the cold nuclear effect contribution.

【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O572.2
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本文編號：1635288