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Register a new userCalculation of prompt diphoton production cross sections at Tevatron and LHC energies
حساب إجمالي إشعاع الضوء الثنائي الفوري في طاقات تيفاترون وطاقات لوحة السيطرة
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أقدم الحالي حسابا متفرقا كاملا في الكيمياء الكمونولوجية الكمونولوجية الكمونولوجية القوية لإنتاج أزواج الطيف الضخم في المجمعات الهادونية. تشمل جميع المساهمات التالية للطبقة التالية من الأزواج الكواكبية والأزواج الأنتيكواكبية والأزواج الجلوونية - (أنتي) كواكبية والأزواج الجلوونية - جلوونية، فضلا عن إعادة ترتيب جميع الطبقات للإشعاع الأولي الذي ينطبق على دقة مستوى السطور التالية التالية. وتحدد منطقة المساحة الفاصلة التي يتم فيها أكثر دقة في الحساب. وتم إثبات التوافق الجيد مع البيانات من Fermilab Tevatron، وتم تقديم التنبؤات لاختبارات أكثر تفصيلا مع بيانات CDF و DO. وتم عرض التنبؤات للتوزيعات لأزواج الطيف المنتجة على طاقة مجمع الحصار الكبير (LHC). وتم مقارنة التوزيعات لأزواج الطيف الناتجة من فسخ هيجس بالتوزيعات الناتجة من عمليات QCD في LHC، مما يظهر أن يمكن الحصول على حساسية محسنة للإشارة مع اختيار محدد للأحداث.
A fully differential calculation in perturbative quantum chromodynamics is presented for the production of massive photon pairs at hadron colliders. All next-to-leading order perturbative contributions from quark-antiquark, gluon-(anti)quark, and gluon-gluon subprocesses are included, as well as all-orders resummation of initial-state gluon radiation valid at next-to-next-to-leading logarithmic accuracy. The region of phase space is specified in which the calculation is most reliable. Good agreement is demonstrated with data from the Fermilab Tevatron, and predictions are made for more detailed tests with CDF and DO data. Predictions are shown for distributions of diphoton pairs produced at the energy of the Large Hadron Collider (LHC). Distributions of the diphoton pairs from the decay of a Higgs boson are contrasted with those produced from QCD processes at the LHC, showing that enhanced sensitivity to the signal can be obtained with judicious selection of events.
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We present results for the SM and MSSM Higgs-boson production cross sections at the Tevatron and the LHC. The SM cross sections are a compilation of the state-of-the-art theoretical predictions. The MSSM cross sections are obtained from the SM ones by means of an effective coupling approximation, as implemented in FeynHiggs. Numerical results have been obtained in four benchmark scenarios for two values of tan beta, tan beta = 5, 40.
We update the theoretical predictions for direct Y(nS) hadroproduction in the framework of NRQCD. We show that the next-to-leading order corrections in alpha_s to the color-singlet transition significantly raise the differential cross section at high pT and substantially affect the polarization of the Upsilon. Motivated by the remaining gap between the NLO yield and the cross section measurements at the Tevatron, we evaluate the leading part of the alpha_s^5 contributions, namely those coming from Y(nS) associated with three light partons. The differential color-singlet cross section at alpha_s^5 is in substantial agreement with the data, so that there is no evidence for the need of color-octet contributions. Furthermore, we find that the polarization of the Y(nS) is longitudinal. We also present our predictions for Y(nS) production at the LHC.
Inclusive bottomonium hadroproduction at the Tevatron is firstly examined in a Monte Carlo framework with the colour-octet mechanism implemented in the event generation. We extract some NRQCD colour-octet matrix elements relevant for $Upsilon(1S)$ hadroproduction. Remarkably we find a quite small contribution (compatible with zero) from feeddown of $chi_{bJ}$ states produced through the colour-octet mechanism: $Upsilon(1S)$ indirect production via $chi_{bJ}$ decays should be mainly ascribed to the colour-singlet model. Finally we extrapolate to LHC energies to predict prompt $Upsilon(1S)$ production rates.
We study the production of prompt diphotons in the central region of rapidity within the framework of the quasi-multi-Regge-kinematics approach applying the hypothesis of quark and gluon Reggeization. We describe accurately and without free parameters the experimental data which were obtained by the CDF Collaboration at the Tevatron Collider. It is shown that the main contribution to studied process is given by the direct fusion of two Reggeized gluons into a photon pair, which is described by the effective Reggeon-Reggeon to particle-particle vertex. The contribution from the annihilation of Reggeized quark-antiquark pair into a diphoton is also considered. At the stage of numerical calculations we use the Kimber-Martin-Ryskin prescription for unintegrated quark and gluon distribution functions, with the Martin-Roberts-Stirling-Thorne collinear parton densities for a proton as input.
Now that the Higgs particle has been observed by the ATLAS and CMS experiments at the LHC, the next endeavour would be to probe its fundamental properties and to measure its couplings to fermions and gauge bosons with the highest possible accuracy. However, the measurements will be limited by significant theoretical uncertainties that affect the production cross section in the main production channels as well as by experimental systematical errors. Following earlier work, we propose in this paper to consider ratios of Higgs production cross sections times decay branching ratios in which most of the theoretical uncertainties and some systematical errors, such as the ones due to the luminosity measurement and the Higgs decay branching fractions, cancel out. The couplings of the Higgs particle could be then probed in a way that will be mostly limited by the statistical accuracy achievable at the LHC and accuracies at the percent level are foreseen for some of the ratios at the end of the LHC run. At the theoretical level, these ratios are also interesting as they do not involve the ambiguities that affect the Higgs total decay width in new physics scenarios. To illustrate how these ratios can be used to determine the Higgs couplings, we perform a rough analysis of the recent ATLAS and CMS data which shows that there is presently no significant deviation from the Standard Model expectation.
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