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"Nuclear structure"
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Grace in all simplicity : beauty, truth, and wonders on the path to the Higgs boson and new laws of nature
\"Grace in All Simplicity narrates the saga of how we have prospected for some of Nature's most tightly held secrets, the basic constituents of matter and the fundamental forces that rule them. Our current understanding of the world (and universe) we inhabit is the result of curiosity, diligence, and daring, of abstraction and synthesis, and of an abiding faith in the value of exploration. In these pages we will meet scientists of both past and present. These men and women are professional scientists and amateurs, the eccentric and the conventional, performers and introverts\"-- Provided by publisher.
Book
Measures of azimuthal anisotropy in high-energy collisions
Azimuthal anisotropy is a key observation made in ultrarelativistic heavy-ion collisions. This phenomenon has played a crucial role in the development of the field over the last two decades. In addition to its interest for studying the quark-gluon plasma, which was the original motivation, it is sensitive to the properties of incoming nuclei, in particular to the nuclear deformation and to the nuclear skin. The azimuthal anisotropy is therefore of crucial importance when relating low-energy nuclear structure to high-energy nuclear collisions. This article is an elementary introduction to the various observables used in order to characterize azimuthal anisotropy, which go under the names of
v
2
{
2
}
,
v
3
{
2
}
,
v
2
{
4
}
, etc. The intended audience is primarily physicists working in the field of nuclear structure.
Journal Article
History of the concept of nuclear shape
This article provides a comprehensive review of the evolution of the nuclear shape concept, a cornerstone in nuclear physics. Tracing its historical development from the early 20th century, we highlight key milestones and paradigm shifts that have shaped our understanding. The review explores the transition from the initial spherical model to the introduction of nuclear deformation, emphasizing the contributions of the liquid drop model and the unified model. The pivotal role of nuclear shapes in elucidating various nuclear phenomena and their profound impact on both theoretical and experimental nuclear physics are discussed in depth. The article underscores the relevance of nuclear shape in contemporary physics, particularly in light of groundbreaking findings from ultra-relativistic heavy ion collisions. These recent results illustrate the enduring significance of nuclear shape in advancing our comprehension of nuclear structure and reactions.
Journal Article
Generic multi-particle transverse momentum correlations as a new tool for studying nuclear structure at the energy frontier
The mean transverse momentum of produced particles,
[
p
T
]
, and its event-by-event fluctuations give direct access to the initial conditions of ultra-relativistic heavy-ion collisions and help probe the colliding nuclei’s structure. The
[
p
T
]
fluctuations can be studied via multi-particle
p
T
correlations; so far, only the lowest four orders have been studied. Higher-order fluctuations can provide stronger constraints on the initial conditions and improved sensitivity to the detailed nuclear structure; however, their direct implementation can be challenging and is still lacking. In this paper, we apply a generic recursive algorithm for the genuine multi-particle
p
T
correlations, which enables the accurate study of higher-order
[
p
T
]
fluctuations without heavy computational cost for the first time. With this algorithm, we will examine the power of multi-particle
p
T
correlations through Monte Carlo model studies with different nuclear structures. The impact on the nuclear structure studies, including the nuclear deformation and triaxial structure, will be discussed. These results demonstrate the usefulness of multi-particle
p
T
correlations for studying nuclear structure in high-energy nuclei collisions at RHIC and the LHC, which could serve as a complementary tool to existing low-energy nuclear structure studies.
Journal Article
A study of nuclear structure of light nuclei at the electron–ion collider
Understanding the substructure of atomic nuclei, particularly the clustering of nucleons inside them, is essential for comprehending nuclear dynamics. Various cluster configurations can emerge depending on excitation energy, the number and types of core clusters, and the presence of excess neutrons. Despite the prevalence of tightly bound cluster formations in low-lying states, understanding the correlation between clusters and their formation mechanisms remains incomplete. This exploring study investigates nuclear clustering at the electron–ion collider (EIC) using simulations based on the modified BeAGLE model. By simulating collisions involving
e
+
9
Be,
e
+
12
C, and
e
+
16
O nuclei, we find that the average energy of particles
⟨
E
⟩
and the system size ratios of particles at forward rapidity exhibit sensitivity to alpha clustering and its various configurations. These findings offer valuable insights into the dynamics of nuclear clustering and its implications for future studies at the EIC.
Journal Article
Probe nuclear structure using the anisotropic flow at the Large Hadron Collider
Recent studies have shown that the shape and radial profile of the colliding nuclei have strong influences on the initial condition of the heavy ion collisions and the subsequent development of the anisotropic flow. Using A Multi-Phase Transport model (AMPT) model, we investigated the impact of nuclear quadrupole deformation
β
2
and nuclear diffuseness
a
0
of
129
Xe on various of flow observables in Xe–Xe collisions at
s
NN
=
5.44 TeV. We found that
β
2
has a strong influence on central collisions while
a
0
mostly influences the mid-central collisions. The relative change of flow observables induced by a change in
β
2
and
a
0
are also found to be insensitive to the values of parameters controlling the strength of the interaction among final state particles. Our study demonstrates the potential for constraining the initial condition of heavy ion collisions using future system scans at the LHC.
Journal Article
Methods for systematic study of nuclear structure in high-energy collisions
There is increasing interest in using high-energy collisions to probe the structure of nuclei, in particular with the high-precision data made possible by collisions performed with pairs of isobaric species. A systematic study requires a variation of parameters representing nuclear properties such as radius, skin thickness, angular deformation, and short-range correlations, to determine the sensitivity of the various observables on each of these properties. In this work we propose a method for efficiently carrying out such study, based on the shifting of positions of nucleons in Monte-Carlo samples. We show that by using this method, statistical demands can be dramatically reduced — potentially reducing the required number of simulated events by orders of magnitude — paving the way for systematic study of nuclear structure in high-energy collisions.
Journal Article
Nuclear structure advancements with multi-nucleon transfer reactions
Multi-Nucleon Transfer (MNT) reactions have been used for decades as a reaction mechanism, in order to populate excited states in nuclei far from stability and to perform nuclear structure studies. Nevertheless, the development of set-ups involving high acceptance tracking magnetic spectrometers (mainly existing in Europe), coupled with the Advanced GAmma Tracking Array (AGATA) opens new possibilities, especially if they are used in conjunction with high-intensity stable beams or ISOL RIBs. In this article, we will discuss the capabilities of such set-ups aiming at different goals, including complete information in high-resolution spectroscopy as well as lifetime measurements.
Journal Article
Recruitment to the Nuclear Periphery Can Alter Expression of Genes in Human Cells
The spatial organisation of the genome in the nucleus has a role in the regulation of gene expression. In vertebrates, chromosomal regions with low gene-density are located close to the nuclear periphery. Correlations have also been made between the transcriptional state of some genes and their location near the nuclear periphery. However, a crucial issue is whether this level of nuclear organisation directly affects gene function, rather than merely reflecting it. To directly investigate whether proximity to the nuclear periphery can influence gene expression in mammalian cells, here we relocate specific human chromosomes to the nuclear periphery by tethering them to a protein of the inner nuclear membrane. We show that this can reversibly suppress the expression of some endogenous human genes located near the tethering sites, and even genes further away. However, the expression of many other genes is not detectably reduced and we show that location at the nuclear periphery is not incompatible with active transcription. The dampening of gene expression around the nuclear periphery is dependent on the activity of histone deacetylases. Our data show that the radial position within the nucleus can influence the expression of some, but not all, genes. This is compatible with the suggestion that re-localisation of genes relative to the peripheral zone of the nucleus could be used by metazoans to modulate the expression of selected genes during development and differentiation.
Journal Article
Nuclear Pore Proteins Nup153 and Megator Define Transcriptionally Active Regions in the Drosophila Genome
Transcriptional regulation is one of the most important processes for modulating gene expression. Though much of this control is attributed to transcription factors, histones, and associated enzymes, it is increasingly apparent that the spatial organization of chromosomes within the nucleus has a profound effect on transcriptional activity. Studies in yeast indicate that the nuclear pore complex might promote transcription by recruiting chromatin to the nuclear periphery. In higher eukaryotes, however, it is not known whether such regulation has global significance. Here we establish nucleoporins as a major class of global regulators for gene expression in Drosophila melanogaster. Using chromatin-immunoprecipitation combined with microarray hybridisation, we show that Nup153 and Megator (Mtor) bind to 25% of the genome in continuous domains extending 10 kb to 500 kb. These Nucleoporin-Associated Regions (NARs) are dominated by markers for active transcription, including high RNA polymerase II occupancy and histone H4K16 acetylation. RNAi-mediated knock-down of Nup153 alters the expression of approximately 5,700 genes, with a pronounced down-regulatory effect within NARs. We find that nucleoporins play a central role in coordinating dosage compensation-an organism-wide process involving the doubling of expression of the male X chromosome. NARs are enriched on the male X chromosome and occupy 75% of this chromosome. Furthermore, Nup153-depletion abolishes the normal function of the male-specific dosage compensation complex. Finally, by extensive 3D imaging, we demonstrate that NARs contribute to gene expression control irrespective of their sub-nuclear localization. Therefore, we suggest that NAR-binding is used for chromosomal organization that enables gene expression control.
Journal Article