arXiv subjects

G. Rong

Publications and source records attributed to G. Rong.

10 recordsLinked to original sources

arXiv2019

The mechanism for the exceptionally high tear strength of carbon black/Hevea natural rubber vulcanizates

Natural rubber vucanizates containing 0-50 phr of a fine carbon black (N115,d=27nm) were prepared and tensile strengths of normal (no pre-cut) and edge pre-cut specimens were determined. Normal tensile strengths of all vulcanizates were similar. At the relatively slow strain rate experienced wholesale by normal uncut specimens, all vulcanizates, prior to crack initiation, strain-crystallized sufficiently to be strong. However, pre-cut specimens experience increased strain rate at a cut tip. Magnification of the strain rate increases as cut depth c increases. Fracture in the gum NR and vulcanizates with up to 14 phr of black occurred by simple forward crack growth from a cut tip, and all exhibited a critical cut size, above which strength dropped abruptly. Furthermore, for these lightly filled samples, strength and critical cut size decreased with increased black content. This indicates less strain-crystalliation before rupture of pre-cut specimens, when levels of black are low. This effect is attributerd to rapid straining at a cut tip and hindering of the chain mobility necessary for crystallization. When black content was increased to 15 phr, with 1 mm<c<2 mm, about 50% of specimens retained simple lateral fracture and were weak, but the other 50% developed deviated cracks (knotty tearing) and were significantly stronger than corresponding pre-cut gum specimens, especially at large c. High strength with sufficient black levels are attributed to increased strain-crystallization and super-blunting (multiple cracks) at a cut tip. These inhibit forward crack growth. For carbon black to enhance strain-crystallization relative to the gum, it appears there must be enough of it to form a bound rubber/black network. If the black concentration is less than this percolation threshold, strain-crystallization is hindered at a cut tip.

cond-mat.soft↗

arXiv2014

Determination of $f_+^K(0)$ and Extraction of $|V_{cs}|$ from Semileptonic $D$ Decays

By globally analyzing all existing measured branching fractions and partial rates in different four momentum transfer-squared $q^2$ bins of $D\to Ke^+ν_e$ decays, we obtain the product of the form factor and magnitude of CKM matrix element $V_{cs}$ to be $f_+^K(0)|V_{cs}|=0.717\pm0.004$. With this product, we determine the $D\to K$ semileptonic form factor $f_+^K(0)=0.737\pm0.004\pm0.000$ in conjunction with the value of $|V_{cs}|$ determined from the SM global fit. Alternately, with the product together with the input of the form factor $f_+^K(0)$ calculated in lattice QCD recently, we extract $|V_{cs}|^{D\to Ke^+ν_e}=0.962\pm0.005\pm0.014$, where the error is still dominated by the uncertainty of the form factor calculated in lattice QCD. Combining the $|V_{cs}|^{D_s^+\to\ell^+ν_\ell}=1.012\pm0.015\pm0.009$ extracted from all existing measurements of $D^+_s\to\ell^+ν_\ell$ decays and $|V_{cs}|^{D\to Ke^+ν_e}=0.962\pm0.005\pm0.014$ together, we find the most precisely determined $|V_{cs}|$ to be $|V_{cs}|=0.983\pm0.011$, which improves the accuracy of the PDG'2014 value $|V_{cs}|^{\rm PDG'2014}=0.986\pm0.016$ by $45\%$.

hep-ex↗

arXiv2014

Determination of $f_+^π(0)$ and Extraction of $|V_{cd}|$ from Semileptonic $D$ Decays

By globally analyzing all existing measured branching fractions for $D\to πe^+ν_e$ decays, partial decay rates in different four momentum transfer-squared $q^2$ bins, as well as products of the decay form factor $f_+^π(q^2)$ and the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix element $|V_{cd}|$, we obtain $f_+^π(0)|V_{cd}|=0.1428\pm0.0019$. This product, in conjunction with $|V_{cd}|$ from a global Standard Model fit, implies a value for the $D\toπ$ semileptonic form factor $f_+^π(0)=0.634\pm0.008\pm0.002$, which is consistent within error with those calculated in theory based on QCD, but with higher precision than the most accurate $f_+^π(0)_{\rm LQCD}=0.666\pm0.020\pm0.021$ calculated in LQCD by a factor of 3.3. Alternately, using this product together with the most accurate form factor calculated in LQCD, we find $|V_{cd}|^{D\to πe^+ν_e}=0.2144\pm0.0029_{\rm exp}\pm 0.0093_{\rm LQCD}$. Combining this $|V_{cd}|^{D\to πe^+ν_e}$ together with $|V_{cd}|^{D^+\toμ^+ν_μ}=0.2160\pm0.0049\pm0.0014$ extracted from both the BESIII and CLEO-c measurements of $D^+\toμ^+ν_μ$ decays, we find the most precisely extracted $|V_{cd}|$ to be $|V_{cd}|=0.2157\pm0.0045$ up to date, which improves the accuracy of the PDG'2014 value $|V_{cd}|_{\rm PDG'2014}=0.225\pm0.008$ by over $70%$. Using this $|V_{cd}|$ together with the PDG'2014 $|V_{ud}|$ and $|V_{td}|$, we check for first column unitarity and find $|V_{ud}|^2+|V_{cd}|^2+|V_{td}|^2-1=-0.004\pm0.002$, which deviates from unitarity by $2σ$. In addition, we find the ratio of $f_+^π(0)$ and $D^+$ decay constant $f_{D^+}$ to be $f_+^π(0)/f_{D^+}=(3.11\pm0.08)$ GeV$^{-1}$, which can be used to validate LQCD calculations for these two quantities.

hep-ex↗

arXiv2014

Determinations of quark mixing matrix elements $|V_{cd}|$ and $|V_{cs}|$ from leptonic and semileptonic $D$ Decays

With the recent measurements of purely leptonic $D^+_{(s)}$ decays and semileptonic $D$ decays in conjunction with decay constants $f_{D^+_{(s)}}$ and form factors $f^{π(K)}_+(0)$ calculated in LQCD, we extract the magnitudes of $V_{cd}$ and $V_{cs}$ to be $|V_{cd}|=0.218\pm0.005$ and $|V_{cs}|=0.987\pm0.016$. Compared to those given in PDG2013, the precisions of these newly extracted $|V_{cd}|$ and $|V_{cs}|$ are improved by more than 2.0 and 1.5 factors, respectively. With the newly extracted $|V_{cd}|$ and $|V_{cs}|$ together with other CKM matrix elements given in PDG2013, we check the unitarity of the CKM matrix, which are $|V_{ud}|^2+|V_{cd}|^2+|V_{td}|^2=0.997\pm0.002$, $|V_{us}|^2+|V_{cs}|^2+|V_{ts}|^2=1.027\pm0.032$ and $|V_{cd}|^2+|V_{cs}|^2+|V_{cb}|^2=1.023\pm0.032$.

hep-ex↗

arXiv2011

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

hep-ph↗

arXiv2010

Review of Experimental Studies of $ψ(3770)$ non-$D\bar D$ Decays

We review the progress on experimental studies of the non-$D\bar D$ decays of the $ψ(3770)$ resonance. With the world average of the observed cross sections for $D\bar D$ production measured at 3.773 GeV by the MARK-I, MARK-II, BES and CLEO Collaborations, combined together with the cross section for $ψ(3770)$ production at its peak as well as initial state radiative correction factor, we find that the non-$D\bar D$ branching fraction of $ψ(3770)$ decays is $B[ψ(3770)\to {\rm non}-D\bar D]=(19.8\pm 1.8 \pm 5.6)%$, which is consistent within error with $B[ψ(3770)\to {\rm non}-D\bar D]=(14.7\pm 3.2)%$ measured previously by the BES Collaboration. In addition, a global amplitude analysis of the cross sections for $e^+e^- \to {\rm LH}$ (LH= light hadron) measured by the CLEO Collaboration shows that the light hadron branching fraction of $ψ(3770)$ decays can be as large as about 11%. Combing the totally measured hadronic and electromegnatic transition rate together with the light hadron branching fraction in the decays of $ψ(3770)$ yields the total non-$D\bar D$ branching fraction in the decays of $ψ(3770)$ to be about 13%.

hep-ex↗

arXiv2010

Are there the VP couplings in the psi(3770) non-charmed decays hidden behind the current experiment measurements?

A global analysis of the full amplitudes for $e^+e^- \to$ VP (Vector and Pseudoscalar) channels at $\sqrt{s}$ =3.773 GeV and 3.670 GeV, which were measured by the CLEO-c Collaboration, shows that those measurements are essentially nontrivial for searching for the $ψ(3770)$ non-$D\bar D$ decays. Unlike the nearly negative verdict on the $ψ(3770)$ strong decays to the VP channels in the original analysis of the CLEO-c data, there exist some unusual solutions that predict the remarkable strength of SU(3) symmetry VP decay of $ψ(3770)$ resonance, which give some clue to understand the mechanism of $ψ(3770)$ non-$D\bar D$ decays and to reexplain the well-known $ρ-π$ puzzle in the J/$ψ$ and $ψ(3686)$ decays.

hep-ex↗

arXiv2008

Physics at BES-III

This physics book provides detailed discussions on important topics in $τ$-charm physics that will be explored during the next few years at \bes3 . Both theoretical and experimental issues are covered, including extensive reviews of recent theoretical developments and experimental techniques. Among the subjects covered are: innovations in Partial Wave Analysis (PWA), theoretical and experimental techniques for Dalitz-plot analyses, analysis tools to extract absolute branching fractions and measurements of decay constants, form factors, and CP-violation and \DzDzb-oscillation parameters. Programs of QCD studies and near-threshold tau-lepton physics measurements are also discussed.

hep-ex↗

arXiv2005

Determination of the branching fractions for $ψ(3770) \to D^0 \bar D^0, D^+D^-,D\bar D$ and $ψ(3770) \to {\rm non-}D\bar D$

The branching fractions for $ψ(3770) \to D^0 \bar D^0, D^+D^-,D\bar D$ and $ψ(3770) \to {\rm non-}D\bar D$ are determined based on the cross sections for $ψ(3770)$ and $D \bar D$ production measured by BES Collaboration. From its recent publications we determine the branching fractions for $ψ(3770) \to D^0 \bar D^0, D^+D^-$ and $ψ(3770) \to D\bar D$ to be $(52.2\pm 4.8\pm 5.5)%$, $(37.0 \pm 5.0 \pm 4.3)%$ and $(89.1 \pm 6.9 \pm 9.2)%$, respectively. The latter one implies the branching fraction for $ψ(3770) \to {\rm non-}D\bar D$ to be $(10.9 \pm 6.9 \pm 9.2)%$, corresponding the inclusive ${\rm non-}D \bar D$ partial width $Γ(ψ(3770) \to {\rm non-}D\bar D) = (2.8 \pm 1.8 \pm 2.4)$ MeV. Meanwhile we determine the observed cross section for $non-D\bar D$ event production from $ψ(3770)$ decays to be $σ^{\rm obs}(ψ(3770)\to non-D\bar D) = (0.72 \pm 0.46 \pm 0.62)$ nb.

hep-ex↗

arXiv2004

Recent Bes Results on psi(3770) and D Meson Production and Decay

Using a data sample of 17.7 $\rm pb^{-1}$ collected at 3.773 GeV with the BES-II detector at the BEPC, the cross sections for $D^0 \bar D^{0}$ and $D^+D^-$ productions at 3.773 GeV have been measured. From the data sample about 33 $\rm pb^{-1}$ taken around 3.773 GeV, 3 purely leptonic decay events of $D^+ \to μ^+ν$ are observed. The branching fraction and the decay constant are measured to be $BF(D^+ \to μ^+ν)=(0.120^{+0.092+0.010}_{-0.063-0.009}) %$ and $f_D=(365^{+121+32}_{-113-28})$ MeV. The semileptonic decay branching fractions for $D^0 \to K^-e^+ν$, $D^0 \to π^-e^+ν$ and $D^+ \to \bar K^0 e^+ν$ are measured to be $BF(D^0 \to K^-e^+ν_e)=(3.52 \pm 0.36\pm 0.25)%$, $BF(D^0 \to π^-e^+ν_e)=(0.36 \pm 0.14\pm 0.03)%$ and $BF(D^+ \to \bar K^0 e^+ν_e)=(8.64 \pm 1.51\pm 0.72)%$. The vector form factors are determined to be $|f^K_+(0)| = 0.75 \pm 0.04 \pm 0.03$ and $|f^π_+(0)| = 0.76 \pm 0.15 \pm 0.06$. The ratio of the two form factors is extracted to be $|f^π_+(0)/f^K_+(0)|= 1.01 \pm 0.20 \pm 0.08$. The ratio of the decay widths is measured to be $Γ(D^0 \to K^-e^+ν)/Γ(D^+ \to \bar K^0 e^+ν) =1.04\pm 0.21 \pm 0.08$. From the data sample of about 27 $\rm pb^{-1}$, the evidence of $ψ(3770) \to J/ψπ^+π^-$ non-${D \bar D}$ decay is observed. The branching fraction is determined to be $BF(ψ(3770) \to J/ψπ^+π^-)=(0.34\pm 0.14 \pm 0.08)%$, corresponding to the partial width of $Γ(ψ(3770) \to J/ψπ^+π^-) = (80 \pm 32 \pm 21)$ keV.

hep-ex↗