Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSearch for structure in the $B_s^0pi^pm$ invariant mass spectrum
43
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The $B_s^0pi^pm$ invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to $3$ fb$^{-1}$ of $pp$ collision data at $sqrt{s} = 7$ and $8$ TeV. No significant excess is found, and upper limits are set on the production rate of the claimed $X(5568)$ state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the $B_s^0pi^pm$ final state. The same limits also apply to a possible exotic meson decaying through the chain $B_s^{*0}pi^pm$, $B_s^{*0} to B_s^0 gamma$ where the photon is excluded from the reconstructed decays.
rate research
Read More
The $Upsilon(1S)mu^+mu^-$ invariant-mass distribution is investigated for a possible exotic meson state composed of two $b$ quarks and two $overline{b}$ quarks, $X_{boverline{b}boverline{b}}$. The analysis is based on a data sample of $pp$ collisions recorded with the LHCb detector at centre-of-mass energies $sqrt{s} =$ 7, 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb$^{-1}$. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the $X_{boverline{b}boverline{b}}$ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range $[2.0,5.0]$, and the $X_{boverline{b}boverline{b}}$ state has rapidity in the range $[2.0,4.5]$ and transverse momentum less than 15 GeV/$c$.
The $g$, $h$, and $k$ Dalitz plot parameters, which are coefficients in a series expansion of the squared module of the matrix element $|M(u,v)|^{2} propto 1 + gu + hu^{2} + kv^{2}$ ($u$, $v$ are invariant variables), have been measured for $K^{pm}to pi^{pm} pi^{0} pi^{0}$ decays using $35 GeV/c$ hadron beams at the IHEP (Protvino) accelerator. Dependences of parameters and fit quality on the $pi^0pi^0$ mass cut were investigated. The results point to the important role of $pi^+pi^- to pi^0pi^0$ charge exchange scattering near the $pi^0pi^0$ mass threshold. The comparison of our data with previous measurements is presented.
We report evidence of a narrow structure, $X(5568)$, in the decay sequence $X(5568) rightarrow B_s^0 pi^{pm}$, $B_s^0 rightarrow J/psi phi$, $J/psirightarrow mu^+ mu^-$, $phi rightarrow K^+K^-$. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be $m = 5567.8 pm 2.9 {rm thinspace (stat)} ^{+0.9}_{-1.9} {rm thinspace (syst)}$ MeV/$c^2$ and $Gamma = 21.9 pm 6.4 {rm thinspace (stat)} ^{+5.0}_{-2.5} {rm thinspace (syst)} $ MeV/$c^2$. If the decay is $X(5568) rightarrow B_s^* pi^{pm} rightarrow B_s^0 gamma pi^{pm}$ with an unseen $gamma$, $m(X(5568))$ will be shifted up by $m(B_s^*) - m(B_s^0) sim 49$ MeV/$c^2$. This measurement is based on $10.4~rm{fb^{-1}}$ of $p bar p $ collision data at $sqrt{s}$ = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.
A new baryon state is observed in the $Lambda_b^0pi^+pi^-$ mass spectrum with high significance using a data sample of $pp$ collisions, collected with the LHCb detector at centre-of-mass energies $sqrt{s}=7, 8$ and 13TeV, corresponding to an integrated luminosity of 9fb$^{-1}$. The mass and natural width of the new state are measured to be begin{eqnarray*} m & = & 6072.3 pm 2.9 pm 0.6 pm 0.2 MeV,, Gamma & = & 72 pm 11 pm 2 MeV,, end{eqnarray*} where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the $Lambda_b^0$ baryon mass. The new state is consistent with the first radial excitation of the $Lambda_b^0$ baryon, the $Lambda_b(2S)^0$ resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed $Lambda_b(5912)^0$ and $Lambda_b(5920)^0$ states are also reported.
We present a precise calculation of the dilepton invariant-mass spectrum and the decay rate for $B^pm to pi^pm ell^+ ell^-$ ($ell^pm = e^pm, mu^pm $) in the Standard Model (SM) based on the effective Hamiltonian approach for the $b to d ell^+ ell^-$ transitions. With the Wilson coefficients already known in the next-to-next-to-leading logarithmic (NNLL) accuracy, the remaining theoretical uncertainty in the short-distance contribution resides in the form factors $f_+ (q^2)$, $f_0 (q^2)$ and $f_T (q^2)$. Of these, $f_+ (q^2)$ is well measured in the charged-current semileptonic decays $B to pi ell u_ell$ and we use the $B$-factory data to parametrize it. The corresponding form factors for the $B to K$ transitions have been calculated in the Lattice-QCD approach for large-$q^2$ and extrapolated to the entire $q^2$-region using the so-called $z$-expansion. Using an $SU(3)_F$-breaking Ansatz, we calculate the $B to pi$ tensor form factor, which is consistent with the recently reported lattice $B to pi$ analysis obtained at large~$q^2$. The prediction for the total branching fraction ${cal B} (B^pm to pi^pm mu^+ mu^-) = (1.88 ^{+0.32}_{-0.21}) times 10^{-8}$ is in good agreement with the experimental value obtained by the LHCb Collaboration. In the low $q^2$-region, heavy-quark symmetry (HQS) relates the three form factors with each other. Accounting for the leading-order symmetry-breaking effects, and using data from the charged-current process $B to pi ell u_ell$ to determine $f_+ (q^2)$, we calculate the dilepton invariant-mass distribution in the low $q^2$-region in the $B^pm to pi^pm ell^+ ell^-$ decay. This provides a model-independent and precise calculation of the partial branching ratio for this decay.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
