اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدIn-medium $omega$ mass from the $gamma + Nb to pi^{0}gamma + X$ reaction
109
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Data on the photoproduction of $omega$ mesons on nuclei have been re-analyzed in a search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. First results from the analysis of the data set were published by D. Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 cite{david}, claiming a lowering of the $omega$ mass in the nuclear medium by 14$%$ at normal nuclear matter density. The extracted $omega$ line shape was found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set has been initiated and a new method has been developed to reduce the background and to determine the shape and absolute magnitude of the background directly from the data. Details of the re-analysis and of the background determination are described. The $omega$ signal on the $Nb$ target, extracted in the re-analysis, does not show a deviation from the corresponding line shape on a $LH_2$ target, measured as reference. The earlier claim of an in-medium mass shift is thus not confirmed. The sensitivity of the $omega$ line shape to different in-medium modification scenarios is discussed.
قيم البحث
اقرأ أيضاً
The $e^+e^- to omega pi^0 to pi^0 pi^0 gamma$ process was investigated in the SND experiment at the VEPP-2M collider. A narrow energy interval near the $phi$-meson was scanned. The observed cross-section reveals, at the level of three standard deviat
ion, the interference effect caused by $phi to pi^0pi^0gamma$ decay. The cross-section parameters, as well as the real and imaginary parts of the $phi$-meson related amplitude, were measured.
We report the first experimental measurements of the nine 1-fold differential cross sections for the $gamma p to pi^+pi^-p$ reaction, obtained with the CLAS detector at Jefferson Laboratory. The measurements cover the invariant mass range of the fina
l state hadrons from 1.6~GeV~$<W<$~2.0~GeV. For the first time the photocouplings of all prominent nucleon resonances in this mass range have been extracted from this exclusive channel. Photoproduction of two charged pions is of particular importance for the evaluation of the photocouplings for the $Delta(1620)1/2^-$, $Delta(1700)3/2^-$, $N(1720)3/2^+$, and $Delta(1905)5/2^+$ resonances, which have dominant decays into the $pipi N$ final states rather than the more extensively studied single meson decay channels.
We report the measurement of the ratio $Gamma(eta to pi^+pi^-gamma)/Gamma(eta to pi^+pi^-pi^0)$ analyzing a large sample of $phi to eta gamma$ decays recorded with the KLOE experiment at the DA$Phi$NE $e^+ e^-$ collider, corresponding to an integrate
d luminosity of 558 pb$^{-1}$. The $eta to pi^+pi^-gamma$ process is supposed to proceed both via a resonant contribution, mediated by the $rho$ meson, and a non resonant direct term, connected to the box anomaly. The presence of the direct term affects the partial width value. Our result $R_{eta}=Gamma(eta to pi^+ pi^- gamma)/Gamma(eta to pi^+ pi^- pi^0)= 0.1838pm 0.0005_{stat} pm 0.0030_{syst}$ is in agreement with a recent CLEO measurement, which differs by more 3 $sigma$ from the average of previous results.
Coherent double neutral-pion photoproduction on the deuteron, $gamma{d}${$to$}$pi^0pi^0{d}$, has been experimentally studied at incident photon energies ranging from 0.75 to 1.15 GeV. The total cross section as a function of the $gamma{d}$ center-of-
mass energy shows resonance-like behavior, which peaks at approximately 2.47 and 2.63 GeV. The measured angular distribution of deuteron emission is rather flat, which cannot be reproduced by the kinematics of quasi-free $pi^0pi^0$ production with deuteron coalescence. In $pi^0d $ invariant-mass distributions, a clear peak is observed at $2.14{pm}0.01$ GeV$/c^2$ with a width of $0.09{pm}0.01$ GeV$/c^2$. The spin-parity of this state is restricted to $1^+$, $2^+$ or $3^-$ from the angular distributions of the two $pi^0$s. The present work shows strong evidence for the existence of an isovector dibaryon resonance with a mass of 2.14 GeV$/c^2$. The $2^+$ assignment is consistent with the theoretically predicted ${cal{D}}_{12}$ state, and also with the energy dependence of the $pi{d}$ partial-wave amplitude $^3!P_2$ for the $pi^{pm}d${$to$}$pi^{pm}d$ and $pi^+d${$to$}${pp}$ reactions.
A measurement of the double-polarization observable $E$ for the reaction $gamma pto pi^0 p$ is reported. The data were taken with the CBELSA/TAPS experiment at the ELSA facility in Bonn using the Bonn frozen-spin butanol (C$_4$H$_9$OH) target, which
provided longitudinally-polarized protons. Circularly-polarized photons were produced via bremsstrahlung of longitudinally-polarized electrons. The data cover the photon energy range from $E_gamma =600$~MeV to $E_gamma =2310$~MeV and nearly the complete angular range. The results are compared to and have been included in recent partial wave analyses.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
