arXiv subjects

Wanpeng Tan

Publications and source records attributed to Wanpeng Tan.

17 recordsLinked to original sources

arXiv2023

New pairing mechanism via chiral electron-hole condensation for non-BCS superconductivity

A novel chiral electron-hole (CEH) pairing mechanism is proposed to account for non-BCS superconductivity. In contrast to BCS Cooper pairs, CEH pairs exhibit a pronounced affinity to antiferromagnetism for superconductivity. The gap equations derived from this new microscopic mechanism are analyzed for both s- and d-wave superconductivity, revealing marked departures from the BCS theory. Unsurprisingly, CEH naturally describes superconductivity in strongly-correlated systems, necessitating an exceedingly large coupling parameter ($\lambda>1$ for s-wave and $\lambda>\pi/2$ for d-wave) to be efficacious. The new mechanism provides a better understanding of various non-BCS features, especially in cuprate and iron-based superconductors. In particular, CEH, through quantitative comparison with experimental data, shows promise in solving long-standing puzzles such as the unexpectedly large gap-to-critical-temperature ratio $\Delta_0/T_c$, the lack of gap closure at $T_c$, superconducting phase diagrams, and a non-zero heat-capacity-to-temperature ratio $C/T$ at $T=0$ (i.e., the ``anomalous linear term''), along with its quadratic behavior near $T=0$ for d-wave cuprates.

cond-mat.supr-con↗

arXiv2023

Mirror symmetry for new physics beyond the Standard Model in $4D$ spacetime

The two discrete generators of the full Lorentz group $O(1,3)$ in $4D$ spacetime are typically chosen to be parity inversion symmetry $P$ and time reversal symmetry $T$, which are responsible for the four topologically separate components of $O(1,3)$. Under general considerations of quantum field theory (QFT) with internal degrees of freedom, mirror symmetry is a natural extension of $P$, while $CP$ symmetry resembles $T$ in spacetime. In particular, mirror symmetry is critical as it doubles the full Dirac fermion representation in QFT and essentially introduces a new sector of mirror particles. Its close connection to T-duality and Calabi-Yau mirror symmetry in string theory is clarified. Extension beyond the Standard model can then be constructed using both left- and right-handed heterotic strings guided by mirror symmetry. Many important implications such as supersymmetry, chiral anomalies, topological transitions, Higgs, neutrinos, and dark energy, are discussed.

physics.gen-ph↗

arXiv2023

Neutron lifetime anomaly and mirror matter theory

This paper reviews the puzzles in modern neutron lifetime measurements and related unitarity issues in the CKM matrix. It is not a comprehensive and unbiased compilation of all historic data and studies, but rather a focus on compelling evidence leading to new physics. In particular, the largely overlooked nuances of different techniques applied in material and magnetic trap experiments are clarified. Further detailed analysis shows that the ``beam'' approach of neutron lifetime measurements is likely to give the ``true'' $β$-decay lifetime, while discrepancies in ``bottle'' measurements indicate new physics at play. The most feasible solution to these puzzles is a newly proposed ordinary-mirror neutron ($n-n'$) oscillation model under the framework of mirror matter theory. This phenomenological model is reviewed and introduced, and its explanations of the neutron lifetime anomaly and possible non-unitarity of the CKM matrix are presented. Most importantly, various new experimental proposals, especially lifetime measurements with small/narrow magnetic traps or under super-strong magnetic fields, are discussed in order to test the surprisingly large anomalous signals that are uniquely predicted by this new $n-n'$ oscillation model.

nucl-ex↗

arXiv2020

Neutron-mirror neutron oscillations in stars

Based on a newly proposed mirror-matter model of neutron-mirror neutron ($n-n'$) oscillations [Phys. Lett. B 797, 134921 (2019)], evolution and nucleosynthesis in single stars under a new theory is presented. In the new model, $n-n'$ oscillations are caused by a very small mass difference between particles of the two sectors. The new theory with the new $n-n'$ model can demonstrate the evolution in a much more convincing way than the conventional belief. In particular, many observations in stars show strong support for the new theory and the new $n-n'$ model. For example, progenitor mass limits and structures for white dwarfs and neutron stars, two different types of core collapse supernovae (II-P and II-L), synthesis of heavy elements, pulsating phenomena in stars, etc, can all be easily and naturally explained under the new theory.

astro-ph.SR↗

arXiv2020

Dark energy and spontaneous mirror symmetry breaking

Dark energy is interpreted as the leftover of mostly canceled vacuum energy due to the spontaneous mirror symmetry breaking (SMSB) at the electroweak phase transition. Based on the newly proposed mirror-matter model (M$^3$), the extended standard model with mirror matter (SM$^3$) is elaborated to provide a consistent foundation for understanding dark energy, dark matter, baryogenesis, and many other puzzles. New insights of Higgs, top quark, and lepton masses are presented under SM$^3$ using staged quark condensation and four-fermion interactions for SMSB. In particular, the nature and mass scales of neutrinos are naturally explained under the new theory. The new cosmology model based on SM$^3$ could potentially resolve more cosmic enigmas. The possible underlying principles for SMSB and SM$^3$ of a maximally interacting, supersymmetric, and mirrored world are also discussed.

physics.gen-ph↗

arXiv2020

Laboratory tests of the ordinary-mirror particle oscillations and the extended CKM matrix

The CKM matrix and its unitarity is analyzed by disentangling experimental information obtained from three different particle systems of neutrons, mesons, and nuclei. New physics beyond the Standard Model is supported under the new analysis. In particular, the newly proposed mirror-matter model [Phys. Lett. B 797, 134921 (2019)] can provide the missing physics and naturally extend the CKM matrix. Laboratory experiments with current technology for measuring neutron, meson, and nuclear decays under various scenarios are proposed. Such measurements can provide stringent tests of the new model and the extended CKM matrix.

physics.gen-ph↗

arXiv2020

Invisible decays of neutral hadrons

Invisible decays of neutral hadrons are evaluated as ordinary-mirror particle oscillations using the newly developed mirror matter model. Assuming equivalence of the $CP$ violation and mirror symmetry breaking scales for neutral kaon oscillations, rather precise values of the mirror matter model parameters are predicted for such ordinary-mirror particle oscillations. Not only do these parameter values satisfy the cosmological constraints, but they can also be used to precisely determine the oscillation or invisible decay rates of neutral hadrons. In particular, invisible decay branching fractions for relatively long-lived hadrons such as $K^0_L$, $K^0_S$, $Λ^0$, and $Ξ^0$ due to such oscillations are calculated to be $9.9\times 10^{-6}$, $1.8\times 10^{-6}$, $4.4\times 10^{-7}$, and $3.6\times 10^{-8}$, respectively. These significant invisible decays are readily detectable at existing accelerator facilities.

physics.gen-ph↗

arXiv2020

Neutron-mirror neutron oscillations for solving the puzzles of ultrahigh-energy cosmic rays

Based on a newly proposed mirror-matter model of neutron-mirror neutron ($n-n'$) oscillations, the puzzles related to ultrahigh-energy cosmic rays (UHECRs) are explained. In particular, the phenomena around the Greisen-Zatsepin-Kuzmin (GZK) cutoff for UHECRs can be well understood under the new mirror matter model assuming a mirror-to-ordinary temperature ratio of $T'/T \sim 0.3$. The suppression factor of the GZK effect due to the opacity of cosmic microwave background is calculated and agrees with the observations well. Most of the super-GZK events (i.e., above the GZK cutoff), as predicted in the new model, come from mirror matter sources that are invisible to electromagnetic telescopes and can penetrate the mirror cosmic microwave background at much further distances. Most remarkably, the anti-correlation between super-GZK and sub-GZK events in the hotspot observed by the Telescope Array (TA) collaboration can be naturally understood in this model. The possible correlations between the UHECRs from the TA hotspot and other nearby powerful sources such as high energy neutrinos detected by IceCube, the largest black hole merger (GW170729) observed by LIGO, and the hottest star-forming supercluster Lynx Arc, are discussed as well under the new theory.

astro-ph.HE↗

arXiv2020

No single unification theory of everything

In light of Gödel's undecidability results (incomplete theorems) for math, quantum indeterminism indicates that physics and the Universe may be indeterministic, incomplete, and open in nature, and therefore demand no single unification theory of everything. The Universe is dynamic and so are the underlying physical models and spacetime. As the 4-d spacetime evolves dimension by dimension in the early universe, consistent yet different models emerge one by one with different sets of particles and interactions. A new set of first principles are proposed for building such models with new understanding of supersymmetry, mirror symmetry, and the dynamic phase transition mechanism - spontaneous symmetry breaking. Under this framework, we demonstrate that different models with no theory of everything operate in a hierarchical yet consistent way at different phases or scenarios of the Universe. In particular, the arrow of time is naturally explained and the Standard Model of physics is elegantly extended to time zero of the Universe.

physics.gen-ph↗

arXiv2019

Kaon oscillations and baryon asymmetry of the universe

Baryon asymmetry of the universe (BAU) is naturally explained with $K^0-K^{0'}$ oscillations of a newly developed mirror-matter model and new understanding of quantum chromodynamics (QCD) phase transitions. A consistent picture for the origin of both BAU and dark matter is presented with the aid of $n-n'$ oscillations of the new model. The global symmetry breaking transitions in QCD are proposed to be staged depending on condensation temperatures of strange, charm, bottom, and top quarks in the early universe. The long-standing BAU puzzle can then be understood with $K^0-K^{0'}$ oscillations that occur at the stage of strange quark condensation and baryon number violation via a non-perturbative sphaleron-like (coined "quarkiton") process. Similar processes at charm, bottom, and top quark condensation stages are also discussed including an interesting idea for top quark condensation to break both the QCD global $U_t(1)_A$ symmetry and the electroweak gauge symmetry at the same time. Meanwhile, the $U(1)_A$ or strong CP problem of particle physics is simply solved under the same framework.

physics.gen-ph↗

arXiv2019

Neutron oscillations for solving neutron lifetime and dark matter puzzles

A model of $n-n'$ (neutron-mirror neutron) oscillations is proposed under the framework of the mirror matter theory with slightly broken mirror symmetry. It resolves the neutron lifetime discrepancy, i.e., the 1% difference in neutron lifetime between measurements from "beam" and "bottle" experiments. In consideration of the early universe evolution, the $n-n'$ mass difference is determined to be about $2\times 10^{-6}$ eV/c$^2$ with the $n-n'$ mixing strength of about $2\times 10^{-5}$. The picture of how the mirror-to-ordinary matter density ratio is evolved in the early universe into the observed dark-to-baryon matter density ratio of about 5.4 is presented. Reanalysis of previous data and new experiments that can be carried out under current technology are discussed and recommended to test this proposed model. Other consequences of the model on astrophysics and possible oscillations of other neutral particles are discussed as well.

physics.gen-ph↗

arXiv2019

An efficient method for mapping the 12C+12C molecular resonances at low energies

The 12C+12C fusion reaction is famous for its complication of molecular resonances, and plays an important role in both nuclear structure and astrophysics. It is extremely difficult to measure the cross sections of 12C+12C fusions at energies of astrophysical relevance due to very low reaction yields. To measure the complicated resonant structure existing in this important reaction, an efficient thick target method has been developed and applied for the first time at energies Ec.m.<5.3 MeV. A scan of the cross sections over a relatively wide range of energies can be carried out using only a single beam energy. The result of measurement at Ec.m.= 4.1 MeV is compared with other results from previous work. This method would be useful for searching potentially existing resonances of 12C+12C in the energy range 1 MeV<Ec.m.<3 MeV.

nucl-ex↗

arXiv2017

Quenching Measurements and Modeling of a Boron-Loaded Organic Liquid Scintillator

Organic liquid scintillators are used in a wide variety of applications in experimental nuclear and particle physics. Boron-loaded scintillators are particularly useful for detecting neutron captures, due to the high thermal neutron capture cross section of $^{10}$B. These scintillators are commonly used in neutron detectors, including the DarkSide-50 neutron veto, where the neutron may produce a signal when it scatters off protons in the scintillator or when it captures on $^{10}$B. Reconstructing the energy of these recoils is complicated by scintillation quenching. Understanding how nuclear recoils are quenched in these scintillators is an important and difficult problem. In this article, we present a set of measurements of neutron-induced proton recoils in a boron-loaded organic liquid scintillator at recoil energies ranging from 57--467 keV, and we compare these measurements to predictions from different quenching models. We find that a modified Birks' model whose denominator is quadratic in $dE/dx$ best describes the measurements, with $χ^2$/NDF$=1.6$. This result will help model nuclear recoil scintillation in similar detectors and can be used to improve their neutron tagging efficiency.

physics.ins-det↗

arXiv2015

Scintillation efficiency measurement of Na recoils in NaI(Tl) below the DAMA/LIBRA energy threshold

The dark matter interpretation of the DAMA modulation signal depends on the NaI(Tl) scintillation efficiency of nuclear recoils. Previous measurements for Na recoils have large discrepancies, especially in the DAMA/LIBRA modulation energy region. We report a quenching effect measurement of Na recoils in NaI(Tl) from 3keV$_{\text{nr}}$ to 52keV$_{\text{nr}}$, covering the whole DAMA/LIBRA energy region for light WIMP interpretations. By using a low-energy, pulsed neutron beam, a double time-of-flight technique, and pulse-shape discrimination methods, we obtained the most accurate measurement of this kind for NaI(Tl) to date. The results differ significantly from the DAMA reported values at low energies, but fall between the other previous measurements. We present the implications of the new quenching results for the dark matter interpretation of the DAMA modulation signal.

physics.ins-det↗

arXiv2014

Experimental cross sections of 165Ho(α,n)168Tm and 166Er(α,n)169Yb for optical potential studies relevant for the astrophysical γ-process

Background: Optical potentials are crucial ingredients for the prediction of nuclear reaction rates needed in simulations of the astrophysical γ-process. Associated uncertainties are particularly large for reactions involving α-particles. This includes (γ,α) reactions which are of special importance in the γ-process. Purpose: The measurement of (α,n) reactions allows for an optimization of currently used α-nucleus potentials. The reactions 165Ho(α,n) and 166Er(α,n) probe the optical model in a mass region where γ-process calculations exhibit an underproduction of p nuclei which is not yet understood. Method: To investigate the energy-dependent cross sections of the reactions 165Ho(α,n) and 166Er(α,n) close to the reaction threshold, self-supporting metallic foils were irradiated with α-particles using the FN tandem Van de Graaff accelerator at University of Notre Dame. The induced activity was determined afterwards by monitoring the specific β-decay channels. Results: Hauser-Feshbach predictions with a widely used global α-potential describe the data well at energies where the cross sections are almost exclusively sensitive to the α-widths. Increasing discrepancies appear towards the reaction threshold at lower energy. Conclusions: The tested global α-potential is suitable at energies above 14 MeV, while a modification seems necessary close to the reaction threshold. Since the γ- and neutron width show non-negligible impact on the predictions, complementary data are required to judge whether or not the discrepancies found can to be solely assigned to the α-width.

nucl-ex↗

arXiv2008

The thermonuclear rate for the 19F(a,p)22Ne reaction at stellar temperatures

The $^{19}$F($α$,p)$^{22}$Ne reaction is considered to be one of the main sources of fluorine depletion in AGB and Wolf-Rayet stars. The reaction rate still retains large uncertainties due to the lack of experimental studies available. In this work the yields for both exit channels to the ground state and first excited state of $^{22}$Ne have been measured and several previously unobserved resonances have been found in the energy range E$_{lab}$=792-1993 keV. The level parameters have been determined through a detailed R-matrix analysis of the reaction data and a new reaction rate is provided on the basis of the available experimental information.

nucl-ex↗

arXiv2007

Experimental measurements of the O15(alpha,gamma)Ne19 reaction rate and the stability of thermonuclear burning on accreting neutron stars

Neutron stars in close binary star systems often accrete matter from their companion stars. Thermonuclear ignition of the accreted material in the atmosphere of the neutron star leads to a thermonuclear explosion which is observed as an X-ray burst occurring periodically between hours and days depending on the accretion rate. The ignition conditions are characterized by a sensitive interplay between the accretion rate of the fuel supply and its depletion rate by nuclear burning in the hot CNO cycle and the rp-process. For accretion rates close to stable burning the burst ignition therefore depends critically on the hot CNO breakout reaction, O15(alpha,gamma)Ne19, that regulates the flow between the hot CNO cycle and the rapid proton capture process. Until recently, the O15(alpha,gamma)Ne19-reaction rate was not known experimentally and the theoretical estimates carried significant uncertainties. In this paper we perform a parameter study of the uncertainty of this reaction rate and determine the astrophysical consequences of the first measurement of this reaction rate. Our results corroborate earlier predictions and show that theoretically burning remains unstable up to accretion rates near the Eddington limit, in contrast to astronomical observations.

astro-ph↗