中微子散射研究：中子-质子与质子-质子对发射的比较
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"这篇研究论文探讨了中微子与原子核相互作用时，特别是中微子与中子-质子和质子-质子对散射的现象。在中微子μ-与12 C的散射过程中，研究人员利用相对论介子交换电流模型计算了2p-2h通道中的产率。他们采用相对论的费米气体模型处理了不同动量传递范围的响应函数和截面。研究表明，在这种散射过程中，初始状态的中子-质子对的贡献显著高于质子-质子对。对于电荷交换的中微子散射，即np对（质子-质子）的2p-2h截面比nn对（中子-中子）的2p-2h截面大，这主要由ω和q的依赖性决定。模型中，介子交换电流，尤其是Δ等压线电流，是导致不同核子对发射概率差异的主要原因。此外，文章还分析了交换贡献、轴向和矢量电流效应的影响。该研究发表在Physics Letters B上，是开放访问的，有助于进一步理解中微子与核物质的相互作用机制。"
这篇论文详细阐述了中微子散射中的核子对发射过程，特别是在中子-质子和质子-质子对中的动态。研究者使用了一个创新的理论框架——相对论介子交换电流模型，该模型能够更准确地描述2p-2h通道内的散射事件。通过相对论的费米气体模型，他们计算了不同动量传递条件下的反应率和截面，从而揭示了中子-质子对相对于质子-质子对在散射过程中的优势。
在讨论中，研究者指出，尽管质子-质子对在某些情况下可能有较大的2p-2h截面，但中子-质子对在初始状态中的贡献更为关键。这种差异主要受到ω和四维动量转移q的影响。此外，他们还考察了除介子交换电流外的其他因素，如交换贡献和轴向与矢量电流的效果，这些因素对散射过程中的核子对发射概率有显著影响。
论文的开放获取特性使得全球的研究人员都能访问和利用这些发现，这对于推进中微子物理和核物理领域的研究具有重要意义。它提供了对中微子与原子核相互作用的深入洞察，这对于理解宇宙的基本过程，如中微子振荡和核反应网络，以及可能的新物理现象，如中微子的质量顺序和中微子与暗物质的相互作用，都至关重要。
Physics Letters B 762 (2016) 124–130
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Emission of neutron–proton and proton–proton pairs in neutrino
scattering
I. Ruiz Simo
a
, J.E. Amaro
a,∗
, M.B. Barbaro
b,c
, A. De Pace
c
, J.A. Caballero
d
, G.D. Megias
d
,
T.W. Donnelly
e
a
Departamento de Física Atómica, Molecular y Nuclear, and Instituto de Física Teórica y Computacional Carlos I, Universidad de Granada, Granada 18071, Spain
b
Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, 10125 Torino, Italy
c
INFN, Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy
d
Departamento de Física Atómica, Molecular y Nuclear, Universidad de Sevilla, Apdo. 1065, 41080 Sevilla, Spain
e
Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received
29 July 2016
Received
in revised form 12 September
2016
Accepted
13 September 2016
Available
online 16 September 2016
Editor: W.
Haxton
We use a recently developed model of relativistic meson-exchange currents to compute the neutron–
proton
and proton–proton yields in (ν
μ
, μ
−
) scattering from
12
C in the 2p–2h channel. We compute the
response functions and cross sections with the relativistic Fermi gas model for different kinematics from
intermediate to high momentum transfers. We find a large contribution of neutron–proton configurations
in the initial state, as compared to proton–proton pairs. In the case of charge-changing neutrino scattering
the 2p–2h cross section of proton–proton emission (i.e., np in the initial state) is much larger than for
neutron–proton emission (i.e., two neutrons in the initial state) by a (ω, q)-dependent factor. The different
emission probabilities of distinct species of nucleon pairs are produced in our model only by meson-
exchange
currents, mainly by the isobar current. We also analyze other effects including exchange
contributions and the effect of the axial and vector currents.
© 2016 The Authors. Publishe d by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
The identification of nuclear effects in neutrino scattering is
essential for modern neutrino oscillation experiments [1–7]. In
particular the sensitivity of the neutrino energy reconstruction to
multi-nucleon events has been stressed in recent data analyses [8].
In the MINERvA neutrino experiment an enhanced population of
multi-proton states has been observed between the quasielastic
and peaks. On the other hand, observation of events with a pair
of energetic protons at the interaction vertex accompanying the
muon in
40
Ar(ν
μ
, μ
−
) reaction has been reported in the ArgoNeuT
experiment [9]. From these events several back-to-back nucleon
configurations have been identified and associated with nuclear
mechanisms involving short-range correlated (SRC) neutron–proton
(np) pairs in the nucleus [10]. However in [11] these “hammer
events” have been modeled by a simple pion production and reab-
sorption
model without nucleon–nucleon correlations, suggesting
that the distribution of pp pairs in the final state is less sensi-
*
Corresponding author.
E-mail
address: amaro@ugr.es (J.E. Amaro).
tive to details of the initial pair configuration. In the opinion of
the authors of [11], the events cannot teach us anything significant
about SRC. The NUWRO event generator supports that the excess
of back-to-back events in ArgoNeuT has a kinematic origin and is
not directly related to SRC [12].
SRC
with back-to-back configurations have been also identified
in two-nucleon knock-out electron scattering experiments on
12
C
for high momentum transfer and missing momentum [13,14]. In
this case one expects an excess of np pairs over pp pairs [15,
16].
The experiment reported a number of np pairs 18 times
larger than their pp counterparts. The analysis of these experi-
ments
is compatible with theoretical single-nucleon and nucleon
pair momentum distributions in variational Monte Carlo calcula-
tions,
where the importance of the tensor forces in the ground-
state
correlations of nuclei has been emphasized [17,18]. While the
kinematics of the experiments have been selected to minimize the
contribution from other mechanisms that can induce two-particle
emission, such as meson-exchange currents (MEC) and isobar exci-
tations
[13], the contribution of MEC cannot be ruled out a priori
[19].
In
this work we investigate the relative effect of MEC on the
separate pp and np emission channels in the inclusive 2p–2h neu-
http://dx.doi.org/10.1016/j.physletb.2016.09.021
0370-2693/
© 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.
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