Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe spin parity of $Z_c^-$(4100), $Z_1^+$(4050) and $Z_2^+$(4250)
46
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We conjecture that $Z_c^-$(4100) found by LHCb group from a Dalitz plot analysis of $B^0to eta_c K^+pi^-$ decay is the charge conjugate of $Z_1^+$(4050) observed in $chi_{c1}pi^+$ distribution from Belle collaboration. Some interesting conclusions are inferred from this assumption. The $Z_2$(4250) would be assigned to be a $J^P = 1^+$ or $1^-$ state because of its absence in $eta_{c}pi^-$ invariant mass distribution, while $Z_1^+$(4050)/$Z_c^-$(4100) could be a $0^+$ or $1^-$ state but $2^+$ is unfavored because it would be coupled to $eta_{c}pi$ in $D$-wave. The null observation of $Z_1 Z_2$, $Z_1 Z_1$ and $Z_2 Z_2$ production in $e^+ e^-$ annihilation and $Upsilon(1S,2S)$ decay by Belle collaboration would further allocate the spin parity combination of $Z_1^+$(4050)/$Z_c^-$(4100) and $Z_2$(4250). Our deductions can be used to exclude a set of proposed models and could be further tested by future experiment, e.g. in $gamma gamma$ collisions.
rate research
Read More
The spin and parity of the $Z_c(3900)^pm$ state are determined to be $J^P=1^+$ with a statistical significance larger than $7sigma$ over other quantum numbers in a partial wave analysis of the process $e^+e^-to pi^+pi^-J/psi$. We use a data sample of 1.92 fb$^{-1}$ accumulated at $sqrt{s}=4.23$ and 4.26 GeV with the BESIII experiment. When parameterizing the $Z_c(3900)^pm$ with a Flatte-like formula, we determine its pole mass $M_textrm{pole}=(3881.2pm4.2_textrm{stat}pm52.7_textrm{syst})textrm{MeV}/c^2$ and pole width $Gamma_textrm{pole}=(51.8pm4.6_textrm{stat}pm36.0_textrm{syst})textrm{MeV}$. We also measure cross sections for the process $e^+e^-to Z_c(3900)^+pi^-+c.c.to J/psipi^+pi^-$ and determine an upper limit at the 90% confidence level for the process $e^+e^-to Z_c(4020)^+pi^-+c.c.to J/psipi^+pi^-$.
Two-point diagnostics $Om(z_i,z_j)$ and $Omh^2(z_i,z_j)$ have been introduced as an interesting tool for testing the validity of the $Lambda$CDM model. Quite recently, Sahni, Shafieloo $&$ Starobinsky (2014) combined two independent measurements of $H(z)$ from BAO data with the value of the Hubble constant $H_0$, and used the second of these diagnostics to test the $Lambda$CDM model. Their result indicated a considerable tension between observations and predictions of the $Lambda$CDM model. Since reliable data concerning expansion rates of the Universe at different redshifts $H(z)$ are crucial for the successful application of this method, we investigate both two-point diagnostics on the most comprehensive set of $N=36$ measurements of $H(z)$ coming from the BAO and differential ages (DA) of passively evolving galaxies. We discuss the uncertainties of two-point diagnostics and find that they are strongly non-Gaussian and follow the patterns deeply rooted in their very construction. Therefore we propose that non-parametric median statistics is the most appropriate way of treating this problem. Our results support the claims that $Lambda$CDM is in tension with $H(z)$ data according to the two-point diagnostics developed by Shafieloo, Sahni and Starobinsky. However, other alternatives to the $Lambda$CDM, such as wCDM or CPL models perform even worse. We also notice that there are serious systematic differences between BAO and DA methods which ought to be better understood before $H(z)$ measurements can become competitive to the other probes.
We use a consistent SU(6) extension of the meson-baryon chiral Lagrangian within a coupled channel unitary approach in order to calculate the T-matrix for meson-baryon scattering in s-wave. The building blocks of the scheme are the pion and nucleon octets, the rho nonet and the Delta decuplet. We identify poles in this unitary T-matrix and interpret them as resonances. We study here the non exotic sectors with strangeness S=0,-1,-2,-3 and spin J=1/2, 3/2 and 5/2. Many of the poles generated can be associated with known N, Delta, Sigma, Lambda and Xi resonances with negative parity. We show that most of the low-lying three and four star odd parity baryon resonances with spin 1/2 and 3/2 can be related to multiplets of the spin-flavor symmetry group SU(6). This study allows us to predict the spin-parity of the Xi(1620), Xi(1690), Xi(1950), Xi(2250), Omega(2250) and Omega(2380) resonances, which have not been determined experimentally yet.
The effects of parity violation in the interaction of relativistic polarized protons and deuterons are discussed. Within Glaubers approach, estimates are obtained for P-odd asymmetries in the total and elastic scattering cross sections, in the deuteron dissociation cross section, and in the inelastic cross section with meson production in a final state. It is shown that, from the point of view of the magnitude of the P-odd effects, the interaction of polarized deuterons with unpolarized protons has an advantage over the interaction of polarized protons with unpolarized deuterons. A significant P-odd asymmetry was found in the dissociation channel of the polarized deuteron.
One class of solutions to the strong CP problem relies on generalized parity symmetries. A minimal model of this type, constructed by Babu and Mohapatra and based on a softly broken parity symmetry, has the remarkable property that effective QCD vacuum angle $bartheta$ vanishes up to one-loop order. We compute the leading two-loop contributions to $bartheta$ in this model and estimate subleading contributions. In contrast to previous estimates, we argue that $bar theta$ is not suppressed by the weak scale, and we find contributions of order $10^{-3}$-$10^{-2}$ multiplying unknown mixing angles and phases. Thus the model does not generically address the strong CP problem, but it might be made consistent with $bartheta<10^{-10}$ in some corners of parameter space. For such non-generic parameters, $bartheta$ is still likely to be just below present bounds, and therefore provides the dominant source of hadronic EDMs. We discuss the resulting EDM phenomenology.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
