Target Mass Effects Research Articles

Localized surface plasmon resonance biosensor chip surface modification and signal amplifications toward rapid and sensitive detection of COVID-19 infections

We developed a multi-pronged approach to enhance the detection sensitivity of localized surface plasmon resonance (LSPR) sensor chips to detect SARS-CoV-2. To this end, poly(amidoamine) dendrimers were immobilized onto the surface of LSPR sensor chips to serve as templates to further conjugate aptamers specific for SARS-CoV-2. The immobilized dendrimers were shown to reduce surface nonspecific adsorptions and increase capturing ligand density on the sensor chips, thereby improving detection sensitivity. To characterize the detection sensitivity of the surface-modified sensor chips, SARS-CoV-2 spike protein receptor-binding domain was detected using LSPR sensor chips with different surface modifications. The results showed that the dendrimer-aptamer modified LSPR sensor chip exhibited a limit of detection (LOD) of 21.9 pM, a sensitivity that was 9 times and 152 times more sensitive than the traditional aptamer- or antibody-based LSPR sensor chips, respectively. In addition, detection sensitivity was further improved by combining rolling circle amplification product and gold nanoparticles to further amplify the detection signals by increasing both the target mass and plasmonic coupling effects. Using pseudo SARS-CoV-2 viral particles as detection targets, we demonstrated that this combined signal intensification approach further enhanced the detection sensitivity by 10 folds with a remarkable LOD of 148 vp/mL, making it one of the most sensitive SARS-CoV-2 detection assays reported to date. These results highlight the potential of a novel LSPR-based detection platform for sensitive and rapid detection of COVID-19 infections, as well as other viral infections and point-of-care applications.

Target mass effects in parton quasi-distributions

We study the impact of non-zero (and apparently large) value of the nucleon mass M on the shape of parton quasi-distributions Q(y,p3), in particular on its change with the change of the nucleon momentum p3. We observe that the usual target-mass corrections induced by the M-dependence of the twist-2 operators are rather small. Moreover, we show that within the framework based on parametrizations by transverse momentum dependent distribution functions (TMDs) these corrections are canceled by higher-twist contributions. We identify a novel source of kinematic target-mass dependence of TMDs and build models corrected for such dependence. We find that resulting changes may be safely neglected for p3≳2M.

Target Mass Corrections to QCD Bjorken Sum Rule for Nucleon Spin Structure Functions

We discuss the possible target mass corrections in the QCD analysis of nucleon's spin-dependent structure functions measured in the polarized deep-inelastic leptoproduction. The target mass correction for the QCD Bjorken sum rule is obtained from the Nachtmann moment and its magnitude is estimated employing positivity bound as well as the experimental data for the asymmetry parameters. We also study the uncertainty due to target mass effects in determining the QCD effective coupling constant $\alpha_s(Q^2)$ from the Bjorken sum rule. The target mass effect for the Ellis-Jaffe sum rule is also briefly discussed.

The Jost-Lehmann-Dyson representation and target mass effects

We develop a method for taking target mass effects into account for the structure functions of inelastic lepton-hadron scattering using analytic moments in the variable s instead of the well-known Nachtmann variable ξ and Bjorken variable x. We find new expressions for the structure functions F1, F2, and F3that depend on the target mass and agree with the spectral property.

Target mass corrections for the virtual photon structure functions to the next-to-next-to-leading order in QCD

We investigate target mass effects in the unpolarized virtual photon structure functions ${F}_{2}^{\ensuremath{\gamma}}(x,{Q}^{2},{P}^{2})$ and ${F}_{L}^{\ensuremath{\gamma}}(x,{Q}^{2},{P}^{2})$ in perturbative QCD for the kinematical region ${\ensuremath{\Lambda}}^{2}\ensuremath{\ll}{P}^{2}\ensuremath{\ll}{Q}^{2}$, where $\ensuremath{-}{Q}^{2}(\ensuremath{-}{P}^{2})$ is the mass squared of the probe (target) photon and $\ensuremath{\Lambda}$ is the QCD scale parameter. We obtain the Nachtmann moments for the structure functions and then, by inverting the moments, we get the expressions in closed form for ${F}_{2}^{\ensuremath{\gamma}}(x,{Q}^{2},{P}^{2})$ up to the next-to-next-to-leading order and for ${F}_{L}^{\ensuremath{\gamma}}(x,{Q}^{2},{P}^{2})$ up to the next-to-leading order, both of which include the target mass corrections. Numerical analysis exhibits that target mass effects appear at large $x$ and become sizable near ${x}_{\mathrm{max}}(=1/(1+\frac{{P}^{2}}{{Q}^{2}}))$, the maximal value of $x$, as the ratio ${P}^{2}/{Q}^{2}$ increases.

Structure functions at low [formula omitted]: higher twists and target mass effects

We review the physics of structure functions at low Q 2 , focusing on the phenomenon of quark-hadron duality and the resonance–scaling transition, both phenomenologically and in the context of quark models. We also present a new implementation of target mass corrections to nucleon structure functions which, unlike existing treatments, has the correct kinematic threshold behavior at finite Q 2 in the x → 1 limit.

TARGET MASS EFFECTS IN POLARIZED DEEP INELASTIC SCATTERING

The target mass effects in polarized DIS have been studied. It was demonstrated that taking into account the first-order target mass corrections to g1 a very good approximation of the exact formula is achieved. It was also shown that their magnitude in the pre-asymptotic DIS region is small except for x > 0.65, where their large effect is partially suppressed by the large values of Q2 due to the cut W2 > 4 GeV 2. The difference between the size of the target mass and higher twist corrections is illustrated.

Target mass effects in deep-inelastic scattering on the deuteron

We calculate the effects of the target mass on deep-inelastic electron scattering on targets of spin one such as the deuteron, focusing on the novel structure functions that enter. It is important to understand these effects given the recent Hermes measurements of the b1(x,Q2) structure function of the deuteron. We also derive the spin-one analogues of the Wandzura–Wilczek relations and discuss possible calculations in lattice QCD.

Mass effects in the polarized virtual photon structure

We discuss target mass effects in the polarized virtual photon structure functions $g_1^\gamma (x,Q^2,P^2)$, $g_2^\gamma (x,Q^2,P^2)$ for the kinematic region $\Lambda^2\ll P^2 \ll Q^2$, where $-Q^2 (-P^2)$ is the mass squared of the probe (target) photon. We obtain the expressions for the structure functions in closed form by inverting the Nachtmann moments for the twist-2 and twist-3 operators. Numerical analysis shows that target mass effects appear at large $x$ and become sizable near the maximal value of $x$, as the ratio $P^2/Q^2$ increases. Target mass effects for the QCD sum rules of $g_1^\gamma$ and $g_2^\gamma$ are also investigated.

Target mass effects in polarized virtual photon structure functions

We study target mass effects in the polarized virtual photon structure functions $g_1^\gamma (x,Q^2,P^2)$, $g_2^\gamma (x,Q^2,P^2)$ in the kinematic region $\Lambda^2\ll P^2 \ll Q^2$, where $-Q^2 (-P^2)$ is the mass squared of the probe (target) photon. We obtain the expressions for $g_1^\gamma (x,Q^2,P^2)$ and $g_2^\gamma (x,Q^2,P^2)$ in closed form by inverting the Nachtmann moments for the twist-2 and twist-3 operators. Numerical analysis shows that target mass effects appear at large $x$ and become sizable near $x_{\rm max}(=1/(1+\frac{P^2}{Q^2}))$, the maximal value of $x$, as the ratio $P^2/Q^2$ increases. Target mass effects for the sum rules of $g_1^\gamma$ and $g_2^\gamma$ are also discussed.

Tau neutrino deep inelastic charged current interactions

The nu_mu -> nu_tau oscillation hypothesis will be tested through nu_tau production of tau in underground neutrino telescopes as well as long-baseline experiments. We provide the full QCD framework for the evaluation of tau neutrino deep inelastic charged current (CC) cross sections, including next-leading-order (NLO) corrections, charm production, tau threshold, and target mass effects in the collinear approximation. We investigate the violation of the Albright-Jarlskog relations for the structure functions F_4,5 which occur only in heavy lepton (tau) scattering. Integrated CC cross sections are evaluated naively over the full phase space and with the inclusion of DIS kinematic cuts. Uncertainties in our evaluation based on scale dependence, PDF errors and the interplay between kinematic and dynamical power corrections are discussed and/or quantified.

Extraction of R = sigma(L)/sigma(T) from CCFR nu(mu)-Fe and nu(mu)-Fe differential cross sections.

We report on the extraction of R = sigma(L)/sigma(T) from CCFR nu(mu)-Fe and nu(mu)-Fe differential cross sections. The CCFR differential cross sections do not show the deviations from the QCD expectations that are seen in the CDHSW data at very low and very high x. R as measured in nu(mu) scattering is in agreement with R as measured in muon and electron scattering. All data on R for Q(2)>1 GeV(2) are in agreement with a NNLO QCD calculation which uses NNLO parton distribution functions and includes target mass effects. We report on the first measurements of R in the low x and Q(2)<1 GeV(2) region (where an anomalous large rise in R for nuclear targets has been observed by the HERMES Collaboration).

Target-mass corrections and the Bloom-Gilman duality of the nucleon structure function

The occurrence of the Bloom-Gilman local duality in the low-order moments of the nucleon structure function is investigated for values of the squared four-momentum transfer Q 2 between ∼0.5 and 10 ( GeV/c) 2 . At variance with previous analyses truncated Cornwall-Norton moments, limited to the nucleon-resonance production regions, are considered. The role played by target-mass corrections is illustrated, showing that target-mass effects are necessary (but not sufficient) for producing the observed Bloom-Gilman duality of the nucleon structure function. The possibility of a local duality between the unphysical region at large values of the Nachtmann variable and the nucleon elastic peak contribution is analyzed. It is found that the proton magnetic form factor extracted assuming local duality is significantly below the experimental data at low and intermediate values of Q 2.

Charm in the nucleon

A next-to-leading order analysis of inelastic electroproduction of charm is performed using an interpolating scheme which maps smoothly onto massless QCD evolution at large \(Q^2\) and photon–gluon fusion at small \(Q^2\). In contrast with earlier analyses, this scheme allows the inclusion of quark and target mass effects and heavy quark thresholds, as well as possible non-perturbative, or intrinsic, charm contributions. We find no conclusive evidence in favor of an intrinsic charm component in the nucleon, although several data points which disagree with perturbative QCD expectations will need to be checked by future experiments.

Charm in the nucleon

A next-to-leading order analysis of inelastic electroproduction of charm is performed using an interpolating scheme which maps smoothly onto massless QCD evolution at large $Q^2$ and photon–gluon fusion at small $Q^2$ . In contrast with earlier analyses, this scheme allows the inclusion of quark and target mass effects and heavy quark thresholds, as well as possible non-perturbative, or intrinsic, charm contributions. We find no conclusive evidence in favor of an intrinsic charm component in the nucleon, although several data points which disagree with perturbative QCD expectations will need to be checked by future experiments.

Charm in the nucleon

A next-to-leading order analysis of inelastic electroproduction of charm is performed using an interpolating scheme which maps smoothly onto massless QCD evolution at large Q^2 and photon-gluon fusion at small Q^2. In contrast with earlier analyses, this scheme allows the inclusion of quark and target mass effects and heavy quark thresholds, as well as possible non-perturbative, or intrinsic, charm contributions. We find no conclusive evidence in favor of an intrinsic charm component in the nucleon, although several data points which disagree with perturbative QCD expectations will need to be checked by future experiments.

Target mass effects in polarized deep-inelastic scattering

We present a computation of nucleon mass corrections to nucleon structure functions for polarized deep-inelastic scattering. We perform a fit to existing data including mass corrections at first order in m 2/ Q 2 and we study the effect of these corrections on physically interesting quantities. We conclude that mass corrections are generally small, and compatible with current estimates of higher twist uncertainties, when available.

The non-perturbative effect on R=σL/σT from QCD vacuum

We investigate the non-perturbative effects on the ratio $R=\sigma_L /\sigma_T$ in lepton-nucleon deep inelastic scattering by taking into account the lowest dimensional condensate contributions from the QCD vacuum. By combining conventional perturbative QCD corrections and the Georgi- Politzer target-mass effects with the non-perturbative effects from the QCD vacuum, we give a good description of the $Q^2$ and $x$ dependences of $R$ in comparison with the recent experimental data.

Target mass effects in QCD Bjorken sum rule

We investigate the target mass effects in QCD Bjorken sum rule. The magnitude of the target mass correction is estimated in a variety of methods employing positivity bound as well as the experimental data for the asymmetry parameters. It turns out that the target mass correction is sizable at low Q 2 of the order of a few GeV 2, where the QCD correction is significant. We show that there exists uncertainty due to target mass effects in determining the QCD effective coupling constant α s ( Q 2) from the Bjorken sum rule.

Target Mass Corrections to QCD Bjorken Sum Rule for Nucleon Spin Structure Functions

We discuss the possible target mass corrections in the QCD analysis of nucleon's spin-dependent structure functions measured in the polarized deep-inelastic leptoproduction. The target mass correction for the QCD Bjorken sum rule is obtained from the Nachtmann moment and its magnitude is estimated employing positivity bound as well as the experimental data for the asymmetry parameters. We also study the uncertainty due to target mass effects in determining the QCD effective coupling constant $\alpha_s(Q^2)$ from the Bjorken sum rule. The target mass effect for the Ellis-Jaffe sum rule is also briefly discussed.