arXiv subjects

Syed Afsar Abbas

Publications and source records attributed to Syed Afsar Abbas.

13 recordsLinked to original sources

arXiv2020

Connection between missing-charge in quasielastic electron scattering and two(one) proton knockout reactions and the island-of-inversion

Our model, based on Quantum Chromodynamics, emphasizes the role of triton clustering in nuclei. As there is good empirical support of triton clustering in nuclei, we may even treat this as a good phenomenological working hypothesis as well. Here we show how our model finds remarkable success in being able to provide a consistent and interconnected understanding of such diverse empirical realities as the missing electric-charge in quasielastic electron scattering, and simultaneously, also the puzzling data within the studies of exotic nuclei. This gives us confidence, that our model should be taking account of the correct and proper degrees of freedom, to physically specify and explain, the total physical reality as manifested in the nuclear medium.

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arXiv2020

Towards a consistent understanding of the exotic nucleus $^{42}_{14}Si_{28}$

The issue of whether $^{42}_{14}Si_{28}$ is doubly magical or not has been a contentious one. Fridmann {\it et al.} (Nature 435 (2005) 922) through studies of two-proton knockout reaction $^{44}_{16}S_{28} \rightarrow ^{42}_{14}Si_{28}$, presented a strong empirical evidence in support of magicity and sphericity of $^{42}_{14}Si_{28}$. However in complete conflict with this, Bastin {\it et al.} (Phys. Rev. Lett. 99 (2007) 022503) gave equally strong empirical evidences, to show that the N = 28 magicity had completely collapsed, and that $^{42}_{14}Si_{28}$ was a well deformed nucleus. At present the popular consensus (Gade {\it et al.}, Phys. Rev. Lett. 122 (2019) 222501) strongly supports the latter one and discards the former one. Here, while we accept the latter experiment as being fine and good, through a careful study of an RMF model calculation, we show that actually the experimental results of Fridmann are also independently good and consistent. As per the Fridmann experiment, the sphericity and magicity of $^{42}_{14}Si_{28}$ is manifested only through proton number Z=14 being a strong magic number, while the neutron magic number N=28 disappears (or goes into hiding); and still this nucleus is spherical. This is a new and amazing property manifesting itself in this exotic nucleus $^{42}_{14}Si_{28}$. In this paper we provide a consistent understanding of this novel reality within a QCD based model. This model, which has been successful in explanation of the halo phenomenon in exotic nuclei, comes forward to provide the physical reason as to why the Fridmann experiment is correct. This QCD based model shows that it is tritons, as elementary entity making up $^{42}_{14}Si_{28}$, which then provides consistency to the above amazing conclusions arising from the Fridmann experiment.

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arXiv2020

Extremely large matter radii in $^{49-51}$Ca isotopes and the $0^{+}$ breathing mode states of $^{48}$Ca

Through inelastic scattering cross section measurements for $^{42-51}$Ca on a carbon target at 280 MeV/nucleon recently, Tanaka {\it et al.} [ arXiv:1911.05262 [nucl-ex]], in a very significant experiment, have demonstrated large swelling of doubly magic $^{48}$Ca core in calcium isotopes beyond N=28. The matter radii observed in these experiments, are surprisingly much larger than the corresponding, already amazingly large charge radii of the same calcium isotopes, by Garcia {\it et al.} [Nat. Phys. 12 (2016) 594]. Here we propose a novel solution, wherein the breathing mode states $0^{+}$ of $^{48}$Ca, provide a global and consistent solution of this matter radii conundrum.

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arXiv2019

Fusion of halo nucleus $^{6}He$ on $^{238}U$: evidence for tennis-ball (bubble) structure of the core of the halo (even the giant-halo) nucleus

In a decade-and-a-half old experiment, Raabe et al.(Nature 431 (2004) 823), had studied fusion of an incoming beam of halo nucleus $^{6}He$ with the target nucleus $^{238}U$. We extract a new interpretation of the experiment, different from the one that has been inferred so far. We show that their experiment is actually able to discriminate between the structures of the target nucleus (behaving as standard nucleus with density distribution described with canonical RMS radius r = $r_0 A^{\frac{1}{3}}$ with $r_0$ = 1.2 fm), and the {\bf "core"} of the halo nucleus, which surprisingly, does not follow the standard density distribution with the above RMS radius. In fact the core has the structure of a tennis-ball (bubble) like nucleus, with a "hole" at the centre of the density distribution. This novel interpretation of the fusion experiment provides an unambigous support to an almost two decades old model (Abbas, Mod. Phys. Lett. A 16 (2001) 755), of the halo nuclei. This Quantum Chromodyanamics based model, succeeds in identifyng all known halo nuclei and makes clear-cut and unique predictions for new and heavier halo nuclei. This model supports the existence of tennis-ball (bubble) like core, of even the giant-neutron halo nuclei. This should prove beneficial to the experimentalists, to go forward more confidently, in their study of exotic nuclei.

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arXiv2019

Puzzling Radii of Calcium Isotopes: $^{40}{\rm Ca} \rightarrow ^{44}{\rm Ca} \rightarrow ^{48}{\rm Ca} \rightarrow ^{52}{\rm Ca}$, and Duality in the Structure of $^{42}_{14}{\rm Si}_{28}$ and $^{48}_{20}{\rm Ca}_{28}$

In this paper we study the issue of the puzzle of the radii of calcium isotopes. Despite an excess of eight neutrons, strangely $^{48}{\rm Ca}$ exhibits essentially the same charge radius as $^{40}{\rm Ca}$ does. A fundamental microscopic description of this is still lacking. Also strange is a peak in charge radius of calcium at N = 24. The $^{52}{\rm Ca}$ (N = 32) nucleus, well known to be doubly magical, amazingly has recently been found to have a very large charge radius. Also amazing is the property of $^{42}_{14}{\rm Si}_{28}$ which simultaneously appears to be both magical/spherical and strongly deformed as well. We use a Quantum Chromodynamics based model, which treats triton as elementary entity to make up $^{42}_{14}{\rm Si}_{28}$. We show here how this QCD based model is able to provide a consistent physical understanding of simultaneity of magicity/sphericity and strong deformation of a single nucleus. This brings in an essential duality in the structure of $^{42}_{14}{\rm Si}_{28}$ and subsequently also that of $^{48}_{20}{\rm Ca}_{28}$ We also provide consistent understanding of the puzzling radii of calcium isotopes. We predict that the radius of $^{54}{\rm Ca}$ should be even bigger than that of $^{52}{\rm Ca}$; and also that the radius of $^{60}{\rm Ca}$ should be the same as that of $^{40}{\rm Ca}$. In addition we also show wherefrom arises the neutron E2 effective charge of $\frac{1}{2}$.

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arXiv2018

The role of the elemental nature of A=3 nuclei in neutron-rich nuclei

The idea of treating the trinucleon systems as elementary entities in the elementary particle model (EPM) as an Effective Field Theory has been a success in explaining the weak charge-changing processes in nuclei. The EPM results are found to be as good as those obtained from nuclear microscopic models using two- and three-body forces. We extend this concept to investigate the validity of the elemental nature of $A=3$ nuclei through studies of nuclear structure of neutron-rich nuclei. By treating neutron-rich nuclei as primarily made up of tritons as its building blocks, we extract one- and two-triton separation energies of these nuclei. Calculations have been performed here within relativistic mean field (RMF) models with latest interactions. Clear evidence arises of a new shell structure with well-defined predictions of new magic nuclei. These unique predictions have been consolidated by standard one- and two-neutron separation energy calculations. The binding energy per nucleon plots of these nuclei also confirm these predictions. We make unambiguos prediction of six magic nuclei: $_{\:\:8}^{24}{\rm O}_{16}$, $_{20}^{60}{\rm Ca}_{40}$, $_{\:\:35}^{105}{\rm Br}_{70}$, $_{\:\:41}^{123}{\rm Nb}_{82}$, $_{\:\:63}^{189}{\rm Eu}_{126}$ and $_{\:\:92}^{276}{\rm U}_{184}$.

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arXiv2012

Colour Confinement and Deformed Baryons in Quantum Chromodynamics

The confinement of coloured entities in Quantum Chromodynamics (QCD) is traced to colour singletness of the observed entities. This is believed to arise from colour singlet state of quark-antiquark for mesons and a fully colour antisymmetric state for baryons. This demands a spherically symmetric baryon in the ground state. However it is pointed out that a deformed baryon in the ground state has been found to be extremely successful phenomenology. There are convincing experimental supports for a deformed nucleon as well. This means that something has been missed in the fundamental theory. In this paper this problem is traced to a new colour singlet state for baryons which has been missed hitherto and incorporation of which provides a consistent justification of a deformed baryon in the ground state. Interestingly this new colour singlet state is global in nature.

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arXiv2011

On The Structure of A=3 Nuclei

The hole in the charge distribution of $^3{\text He}$ is a major problem in A=3 nuclei. The canonical wavefucntion of A=3 nuclei which does well for electromagnetic properties of A=3 nuclei fails to produce the hole in A=3 nuclei. The hole is normally assumed to arise from explicit quark degree of freedom. Very often quark degrees of freedom are imposed to propose a different short range part of the wavefunction for A=3 to explain the hole in $^3{\text He}$. So an hybrid model with nucleonic degree of freedom in outer part and quark degrees of freedom in the inner part of the nucleus have been invoked to understand the above problem. Here we present a different picture with a new wavefunction working at short range within nucleonic degrees of freedom itself. So the above problem is explained here based entirely on the nucleonic degree of freedom only.

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arXiv2011

On the New Puzzling Results from MiniBooNE

We look into the recent puzzlng results from MiniBooNE and contrast their results with that from NOMAD. A pictuire which provides consistent decscriptiobn of both is discussed here. This also points to future directions in neutrino studies.

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arXiv2010

A=3 Clustering in Nuclei

Alpha clustering in nuclei, at present is a well studied and reasonably well accepted property of the nucleus. Less well appreciated and more ambiguous is the role of A=3 clustering, i.e. helion and triton, in nuclei. Here we try to place A=3 clustering in nuclei into its proper perspective, first by pointing out strong experimental evidences which indicate its clear presence in nuclei and secondly showing as to how to include these A=3 clusters in a proper and consistent theoretical understanding of the nuclear phenomenon.

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arXiv2009

What the Right Handed Neutrino Really is?

We look into the concept of electric charge quantization in the Standard Model. The role of the vector nature of electromagnetism and that of mass generation by Yukawa coupling is studied. We show how the baryon and the lepton numbers arise naturally in this picture. This points to an unambiguous and fundamental understanding of the actual nature of the right-handed neutrino. This conforms to Wigner's analysis of the irreducible representations of the Poincare group.

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arXiv2009

An Alternative Framework of Geometry and Topology in Relativity

We study geometry and topology as complementary and dual aspects of the mathematical space. The same is used to get a better understanding of the Cosmological Constant. Having failed so far to include gravity in a proper unified framework with the other three fundamental gauge forces, we are now faced with an additional unwanted fifth force of repulsion, also envisaged as the Dark Energy problem. How does one understand this 3+1+1 fundamental force dilemma? We introduce here a novel idea of the Fundamental Forces. This will give us an additional and an all-encompassing way of classifying these five fundamental forces in a consistent manner and thereby strengthen the geometry-topology complementarity concept. This also helps us to understand as to what one actually means when substituting ${g_{μν}} = {η_{μν}} + {h_{μν}}$ with the last term being "small" in General Relativity. This provides an understanding of the generic relationship and the complementarity of the geometric and the topological structures which is then formalized as a basic theorem enabling us to understand the underlying connection between the physical reality and the pure mathematical structures.

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arXiv2008

Whither Nuclear Physics ?

Nuclear Physics has had its ups and downs. However in recent years, bucked up by some new and often puzzling data, it has become a potentially very rich field. We review some of these exciting developments in a few important sectors of nuclear physics. Emphasis shall be on the study of exotic nuclei and the new physics that these nuclei are teaching us.

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