arXiv subjects

Yu Jia

Publications and source records attributed to Yu Jia.

At least 109 records · Page 6Linked to original sources

arXiv2017

Next-to-next-to-leading-order QCD corrections to hadronic width of pseudoscalar quarkonium

We compute the next-to-next-to-leading order (NNLO) QCD corrections to the hadronic decay rates of the pseudoscalar quarkonia, at the lowest order in velocity expansion. The validity of NRQCD factorization for inclusive quarkonium decay process, for the first time, is verified to relative order $α_s^2$. As a byproduct, the renormalization group equation (RGE) of the leading NRQCD 4-fermion operator ${\cal O}_1({}^1S_0)$ is also deduced to this perturbative order. By incorporating this new piece of correction together with available relativistic corrections, we find that there exists severe tension between the state-of-the-art NRQCD predictions and the measured $η_c$ hadronic width, and in particular the branching fraction of $η_c\to γγ$. NRQCD appears to be capable of accounting for $η_b$ hadronic decay to a satisfactory degree, and our most refined prediction is ${\rm Br}(η_b\to γγ) = (4.8\pm 0.7)\times 10^{-5}$.

hep-ph↗

arXiv2017

Mixed electroweak-QCD corrections to $e^+e^-\to HZ$ at Higgs factory

The prospective Higgs factories, exemplified by ILC, FCC-ee and CEPC, plan to conduct the precision Higgs measurements at the $e^+e^-$ center-of-mass energy around 250 GeV. The cross sections for the dominant Higgs production channel, the Higgsstrahlung process, can be measured to a (sub-) percent accuracy. Merely incorporating the well-known next-to-leading order (NLO) electroweak corrections appears far from sufficient to match the unprecedented experimental precision. In this work, we make an important advancement toward this direction by investigating the mixed electroweak-QCD corrections to $e^+e^-\to HZ$ at next-to-next-to-leading order (NNLO) for both unpolarized and polarized $Z$ boson. The corrections turn out to reach one percent level of the Born-order results, thereby must be incorporated in the future confrontation with the data.

hep-ph↗

arXiv2017

Density-functional calculations of multivalency-driven formation of Te-based monolayer materials with superior electronic and optical properties

Contemporary science is witnessing a rapid expansion of the two-dimensional (2D) materials family, each member possessing intriguing emergent properties of fundamental and practical importance. Using the particle-swarm optimization method in combination with first-principles density functional theory calculations, here wepredict a new category of 2D monolayers named tellurene, composed of the metalloid element Te, with stable 1T-MoS2-like ( α-Te), and metastable tetragonal (\b{eta}-Te) and 2H-MoS2-like (γ-Te) structures. The underlying formation mechanism of such tri-layer arrangements is uniquely rooted in the multivalent nature of Te, with the central-layer Te behaving more metal-like (e.g., Mo), and the two outer layers more semiconductor-like (e.g.,S). In particular, the α-Te phase can be spontaneously obtained from the magic thicknesses truncated along the [001] direction of the trigonal structure of bulk Te. Furthermore, both the α- and \b{eta}-Te phases possess electron and hole mobilities much higher than MoS2, as well as salient optical absorption properties. These findings effectively extend the realm of 2D materials to group-VI monolayers, and provide a new and generic formation mechanism for designing 2D materials.

cond-mat.mes-hall↗

arXiv2016

Relativistic correction to gluon fragmentation function into pseudoscalar quarkonium

Inspired by the recent measurements of the $η_c$ meson production at LHC, we investigate the relativistic correction effect for the fragmentation function of the gluon into $η_c$, which constitutes the crucial nonperturbative elements to understand $η_c$ production at high $p_T$. Employing three distinct methods, we calculate the leading relativistic correction to the $g\toη_c$ fragmentation function in the NRQCD factorization framework, as well as verify the existing NLO result for the $c\to η_c$ fragmentation function. We also study the evolution behavior of these fragmentation functions with the aid of DGLAP equation.

hep-ph↗

arXiv2016

Spin-orbit coupling effects on the stability of two competing structures in Pb/Si(111) and Pb/Ge(111)

Using first-principles density-functional theory (DFT) calculations, we investigate the 4/3-monolayer structure of Pb on the Si(111) or Ge(111) surface within the two competing structural models termed the H$_3$ and T$_4$ structures. We find that the spin-orbit coupling (SOC) influences the relative stability of the two structures in both the Pb/Si(111) and Pb/Ge(111) systems: i.e., our DFT calculation without including the SOC predicts that the T$_4$ structure is energetically favored over the H$_3$ structure by $ΔE$ = 25 meV for Pb/Si(111) and 22 meV for Pb/Ge(111), but the inclusion of SOC reverses their relative stability as $ΔE$ = $-$12 and $-$7 meV, respectively. Our analysis shows that the SOC-induced switching of the ground state is attributed to a more asymmetric surface charge distribution in the H$_3$ structure, which gives rise to a relatively larger Rashba spin splitting of surface states as well as a relatively larger pseudo-gap opening compared to the T$_4$ structure. By the nudged elastic band calculation, we obtain a sizable energy barrier from the H$_3$ to the T$_4$ structure as ${\sim}$0.59 and ${\sim}$0.27 eV for Pb/Si(111) and Pb/Ge(111), respectively. It is thus likely that the two energetically competing structures can coexist at low temperatures.

physics.comp-ph↗

arXiv2015

Next-to-next-to-leading-order QCD corrections to $χ_{c0,2}\rightarrow γγ$

We calculate the next-to-next-to-leading-order (NNLO) perturbative corrections to $P$-wave quarkonia annihilation decay to two photons, in the framework of nonrelativistic QCD (NRQCD) factorization. The order-$α_s^2$ short-distance coefficients associated with each helicity amplitude are presented in a semi-analytic form, including the "light-by-light" contributions. With substantial NNLO corrections, we find disquieting discrepancy when confronting our state-of-the-art predictions with the latest \textsf{BESIII} measurements, especially fail to account for the measured $χ_{c2}\toγγ$ width. Incorporating the effects of spin-dependent forces would even exacerbate the situation, since it lifts the degeneracy between the nonperturbative NRQCD matrix elements of $χ_{c0}$ and $χ_{c2}$ toward the wrong direction. We also present the order-$α_s^2$ predictions to $χ_{b0,2}\toγγ$, which await the future experimental test.

hep-ph↗

arXiv2015

Electronic and magnetic properties of dopant atoms in SnSe monolayer: a first-principles study

SnSe monolayer with orthorhombic Pnma GeS structure is an important two-dimensional (2D) indirect band gap material at room temperature. Based on first-principles density functional theory calculations, we present systematic studies on the electronic and magnetic properties of X (X = Ga, In, As, Sb) atoms doped SnSe monolayer. The calculated electronic structures show that Ga-doped system maintains semiconducting property while In-doped SnSe monolayer is half-metal. The As- and Sb- doped SnSe systems present the characteristics of n-type semiconductor. Moreover, all considered substitutional doping cases induce magnetic ground states with the magnetic moment of 1μB. In addition, the calculated formation energies also show that four types of doped systems are thermodynamic stable. These results provide a new route for the potential applications of doped SnSe monolayer in 2D photoelectronic and magnetic semiconductor devices.

physics.comp-ph↗

arXiv2015

Quasi Distribution Amplitude of Heavy Quarkonia

The recently-proposed quasi distributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions (PDF) and distribution amplitudes (DA), directly in the $x$-space. Owing to its excessive simplicity, the heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DA. In the framework of non-relativistic QCD (NRQCD) factorization, we compute the order-$α_s$ correction to both light-cone distribution amplitudes (LCDA) and quasi-DA associated with the lowest-lying quarkonia, with the transverse momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the future lattice study of the quasi distributions.

hep-ph↗

arXiv2015

Can NRQCD explain the $γγ^* \to η_c$ transition form factor data?

Unlike the bewildering situation in the $γγ^*\to π$ form factor, a widespread view is that perturbative QCD can decently account for the recent \textsc{BaBar} measurement of $γγ^*\to η_c$ transition form factor. The next-to-next-to-leading order (NNLO) perturbative correction to the $γγ^*\to η_{c,b}$ form factor, is investigated in the NRQCD factorization framework for the first time. As a byproduct, we obtain by far the most precise order-$α_s^2$ NRQCD matching coefficient for the $η_{c,b}\to γγ$ process. After including the substantial negative order-$α_s^2$ correction, the good agreement between NRQCD prediction and the measured $γγ^*\to η_c$ form factor is completely ruined over a wide range of momentum transfer squared. This eminent discrepancy casts some doubts on the applicability of NRQCD approach to hard exclusive reactions involving charmonium.

hep-ph↗

arXiv2015

Origin of Symmetric Dimer Images of Si(001) Observed in Low-Temperature STM

It has been a long-standing puzzle why buckled dimers of the Si(001) surface appeared symmetric below 20 K in scanning tunneling microscopy (STM) experiments. Although such symmetric dimer images were concluded to be due to an artifact induced by STM measurements, its underlying mechanism is still veiled. Here,we demonstrate, based on a first-principles density-functional theory calculation, that the symmetric dimer images are originated from the flip-flop motion of buckled dimers, driven by quantum tunneling (QT). It is revealed that at low temperature the tunneling-induced surface charging with holes reduces the energy barrier for the flipping of buckled dimers, thereby giving rise to a sizable QT-driven frequency of the flip-flop motion. However, such a QT phenomenon becomes marginal in the tunneling-induced surface charging with electrons. Our findings provide an explanation for low-temperature STM data that exhibits apparent symmetric (buckled) dimer structure in the filled-state (empty-state) images.

cond-mat.mtrl-sci↗

arXiv2015

Dilute magnetic semiconductor and half metal behaviors in 3d transition-metal doped black and blue phosphorenes: a first-principles study

We present first-principles density-functional calculations for the structural, electronic, and magnetic properties of substitutional 3d transition metal (TM) impurities in two-dimensional black and blue phosphorenes. We find that the magnetic properties of such substitutional impurities can be understood in terms of a simple model based on the Hund's rule. The TM-doped black phosphorenes with Ti, V, Cr, Mn, Fe and Ni impurities show dilute magnetic semiconductor (DMS) properties while those with Sc and Co impurities show nonmagnetic properties. On the other hand, the TM-doped blue phosphorenes with V, Cr, Mn and Fe impurities show DMS properties, those with Ti and Ni impurities show half-metal properties, whereas Sc and Co doped systems show nonmagnetic properties. We identify two different regimes depending on the occupation of the hybridized electronic states of TM and phosphorous atoms: (i) bonding states are completely empty or filled for Sc- and Co-doped black and blue phosphorenes, leading to non-magnetic; (ii) non-bonding d states are partially occupied for Ti-, V-, Cr-, Mn-, Fe- and Ni-doped black and blue phosphorenes, giving rise to large and localized spin moments. These results provide a new route for the potential applications of dilute magnetic semiconductor and half-metal in spintronic devices by employing black and blue phosphorenes.

cond-mat.mtrl-sci↗

arXiv2015

Equivalence of Electronic and Mechanical Stresses in Structural Phase Stabilization: A Case Study of Indium Wires on Si(111)

It was recently proposed that the stress state of a material can also be altered via electron or hole doping, a concept termed electronic stress (ES), which is different from the traditional mechanical stress (MS) due to lattice contraction or expansion. Here we demonstrate the equivalence of ES and MS in structural stabilization, using In wires on Si(111) as a prototypical example. Our systematic density-functional theory calculations reveal that, first, for the same degrees of carrier doping into the In wires, the ES of the high-temperature metallic 4x1 structure is only slightly compressive, while that of the low-temperature insulating 8x2 structure is much larger and highly anisotropic. As a consequence, the intrinsic energy difference between the two phases is significantly reduced towards electronically phase-separated ground states. Our calculations further demonstrate quantitatively that such intriguing phase tunabilities can be achieved equivalently via lattice-contraction induced MS in the absence of charge doping. We also validate the equivalence through our detailed scanning tunneling microscopy experiments. The present findings have important implications in understanding the underlying driving forces involved in various phase transitions of simple and complex systems alike.

cond-mat.mes-hall↗

arXiv2015

Anomalous doping effect in black phosphorene from first-principles calculations

Using first-principles density functional theory calculations, we investigate the geometries, electronic structures, and thermodynamic stabilities of substitutionally doped phosphorene sheets with group III, IV, V, and VI elements. We find that the electronic properties of phosphorene are drastically modified by the number of valence electrons in dopant atoms. The dopants with even number of valence electrons enable the doped phosphorenes to have a metallic feature, while the dopants with odd number of valence electrons keep the semiconducting feature with a larger band gap than the undoped phosphorene. This even-odd behavior is attributed to the peculiar bonding characteristics of phosphorene and the strong hybridization of sp orbitals between dopants and phosphorene. The calculated formation energies of various substitutional dopants in phosphorene show that such doped systems can be thermodynamically stable.

physics.comp-ph↗

arXiv2015

Finite volume corrections to the binding energy of the X(3872)

The quark mass dependence of hadrons is an important input for lattice calculations. We investigate the light quark mass dependence of the binding energy of the X(3872) in a finite box to next-to-leading order in an effective field theory for the X(3872) with perturbative pions (XEFT). At this order, the quark mass dependence is determined by a quark mass-dependent contact interaction in addition to the one-pion exchange. While there is only a moderate sensitivity to the light quark masses in the region up to twice their physical value, the finite volume effects are significant already at box length as large as 20 fm.

hep-ph↗

arXiv2014

Short-range force between two Higgs bosons

The $S$-wave scattering length and the effective range of the Higgs boson in Standard Model are studied using effective-field-theory approach. After incorporating the first-order electroweak correction, the short-range force between two Higgs bosons remains weakly attractive for $M_H=126$ GeV. It is interesting to find that the force range is about two order-of-magnitude larger than the Compton wavelength of the Higgs boson, almost comparable with the typical length scale of the strong interaction.

hep-ph↗

arXiv2013

Light quark mass dependence of the X(3872) in XEFT

The quark mass dependence of hadrons is an important input for lattice calculations. We investigate the light quark mass dependence of the binding energy of the X(3872) and the Dbar0-D*0 scattering length in the C=+1 channel to next-to-leading order in XEFT where pion interactions are perturbative. At this order, the quark mass dependence is determined by a quark mass-dependent contact interaction in addition to the one-pion exchange. Using naturalness arguments to constrain unknown parameters, we find a moderate sensitivity of the binding energy for quark masses up to twice the physical value while the scattering length is more sensitive. The occurrence of infrared divergences due to on-shell pions in XEFT and their treatment is discussed in detail.

hep-ph↗

arXiv2013

Some recent progress in understanding exclusive double charmonium production at $B$ factories

We review some recent progress in understanding various exclusive double charmonium production processes at $B$ factories, within the nonrelativistic QCD factorization framework. First we investigate the impact of the joint perturbative and relativistic correction on the process that has attracted a great amount of attention in the past decade, $e^+e^-\to J/ψ+η_c$. We then briefly discuss the phenomenological implication of the next-to-leading order perturbative correction to the processes $e^+e^-\to J/ψ+χ_{c0,1,2} (η_{c2})$. We further emphasize a novel theoretical challenge, which is recently discovered by applying the NRQCD factorization approach to the helicity-suppressed hard exclusive reactions involving heavy quarkonium.

hep-ph↗

arXiv2013

Reconciling the nonrelativistic QCD prediction and the $J/ψ\to 3γ$ data

It has been a long-standing problem that the rare electromagnetic decay process $J/ψ\to 3γ$ is plagued with both large and negative radiative and relativistic corrections. To date it remains futile to make a definite prediction to confront with the branching fraction of $J/ψ\to 3γ$ recently measured by the \textsf{CLEO-c} and \textsf{BESIII} Collaborations. In this work, we investigate the joint perturbative and relativistic correction (i.e. the ${\mathcal O}(α_s v^2)$ correction, where $v$ denotes the characteristic velocity of the charm quark inside the $J/ψ$) for this decay process, which turns out to be very significant. After incorporating the contribution from this new ingredient, with the reasonable choice of the input parameters, we are able to account for the measured decay rates in a satisfactory degree.

hep-ph↗