arXiv 2002.030122020-02hep-phhep-exnucl-exnucl-th

大型强子对撞机上的远向前中微子

Far-forward neutrinos at the Large Hadron Collider

Weidong Bai, Milind Diwan, Maria Vittoria Garzelli, Yu Seon Jeong, Mary Hall Reno

备注：: 39 pages, 16 figures
发表信息：: JHEP06(2020)032
DOI：: 10.1007/JHEP06(2020)032

摘要：

本文对大型强子对撞机（LHC）产生的粲强子和底强子衰变产生的高能中微子能量分布进行了新的计算。在非常向前的rapidities的运动学区域中，重味产生和衰变是τ中微子的来源，导致在距离相互作用区域480 m的1 m长，1 m半径的铅中微子探测器中产生数千个{带电电流} τ中微子事件。在我们的计算中，次主导阶QCD辐射修正占的生产截面。非微扰内禀$k_T$效应近似于一个简单的唯象模型，引入高斯$k_T$涂抹的部分子分布函数，这也可能模仿微扰效应，由于多个初始状态的软胶子发射。从部分子到强子态的转变由唯象碎裂函数描述。为了研究各种输入参数的影响，$D_s^\pm$生产的理论预测进行了比较与LHCb数据的横向动量和快度的双微分截面。与输入参数值的选择，最终影响的τ中微子事件分布的预测，相关的不确定性进行了讨论。我们考虑一个3+1中微子混合的情况下，说明中微子实验的潜力，以限制3+1参数空间使用τ中微子和反中微子。我们发现大的理论不确定性的中微子通量的预测在遥远的向前区域。由于QCD的理论不确定性很大，因此将τ中微子振荡的效应分解为无菌中微子，并将3+1方案与具有三种活性中微子味道的标准方案区分开来将是具有挑战性的。

英文摘要：

We present a new calculation of the energy distribution of high-energy neutrinos from the decay of charm and bottom hadrons produced at the Large Hadron Collider (LHC). In the kinematical region of very forward rapidities, heavy-flavor production and decay is a source of tau neutrinos that leads to thousands of { charged-current} tau neutrino events in a 1 m long, 1 m radius lead neutrino detector at a distance of 480 m from the interaction region. In our computation, next-to-leading order QCD radiative corrections are accounted for in the production cross-sections. Non-perturbative intrinsic-$k_T$ effects are approximated by a simple phenomenological model introducing a Gaussian $k_T$-smearing of the parton distribution functions, which might also mimic perturbative effects due to multiple initial-state soft-gluon emissions. The transition from partonic to hadronic states is described by phenomenological fragmentation functions. To study the effect of various input parameters, theoretical predictions for $D_s^\pm$ production are compared with LHCb data on double-differential cross-sections in transverse momentum and rapidity. The uncertainties related to the choice of the input parameter values, ultimately affecting the predictions of the tau neutrino event distributions, are discussed. We consider a 3+1 neutrino mixing scenario to illustrate the potential for a neutrino experiment to constrain the 3+1 parameter space using tau neutrinos and antineutrinos. We find large theoretical uncertainties in the predictions of the neutrino fluxes in the far-forward region. Untangling the effects of tau neutrino oscillations into sterile neutrinos and distinguishing a 3+1 scenario from the standard scenario with three active neutrino flavours, will be challenging due to the large theoretical uncertainties from QCD.

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