Recent results from SND detector at VEPP-2000 collider

Abstract

Recent results on e+e−annihilation to hadrons from SND experiment at VEPP-2000 collider are presented. Corresponding data set is about 200 pb−1 of integrated luminosity collected at the energy region below 2 GeV. The processes e+e− → π+π− , π0γ, ωπ0, π+π−π0, ηπ+π−π0, η, π+π−4π0 have been studied. Searches for e+e− annihilation to C-even resonances η and f1(1285) were done.

Strong coupling from an improved τ vector isovector spectral function

“…We have recently produced a new vector isovector spectral function based on a combination of the ALEPH and OPAL spectra for the dominant ππ 0 , π3π 0 , and 3ππ 0 τ decay channels, supplemented by the addition of contributions from all numerically significant residual decay modes. The residual modes contributions are obtained entirely from experimental data, using the recent BaBAR spectrum for τ → K − K 0 ν τ [14] and a wealth of recent CVC-related cross-section results from e + e − → hadrons obtained by CMD-3, SND and BaBar [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. This new spectral function is more inclusive than its predecessors, since it contains more residual modes, is solely based on experimental data (with no Monte Carlo simulated channels), and has smaller errors.…”

“…We include, in our new spectral function, the following decay modes: (i) π − ω(→ non-3π), K − K 0 , ηπ − π 0 , K Kπ, 3π − 2π + π 0 , and 2π − π + 3π 0 , which were also included by both the ALEPH and OPAL collaborations, (ii) (3π) − ω(→ non-3π) and K Kππ, included only by ALEPH, and (iii) the small additional contributions from π − 5π 0 and ηωπ + η4π, not included in either of the ALEPH or OPAL analyses. With the exception of the contributions from τ → K − K 0 ν τ , which were measured by BaBar [14], all the other modes are obtained from the respective e + e − cross sections with CVC [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29], applying the necessary corrections for vacuum polarization effects. The individual channels are normalized to the respective BFs described in the 2019 HFLAV compilation [32] (correlations among these values are taken into account).…”

“…First, BaBar has measured the spectrum of τ → K − K 0 ν τ [14]. Second, thanks to a wealth of new experimental measurements of many exclusive-channel cross sections in e + e − → hadrons [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] by the CMD-3, BaBar, and SND collaborations, conserved vector current (CVC) relations allow essentially all remaining vector isovector mode contributions to be obtained using exclusive mode electroproduction cross-section data (with negligible isospin-breaking corrections, as we discuss below). In Ref.…”

BINP electron-positron facilities

“…4. Collider itself hosts two particle detectors [14,15], Spherical Neutral Detector (SND) and Cryogenic Magnetic Detector (CMD-3), placed into dispersion-free low-beta straights. The final focusing (FF) is realized using superconducting 13 T solenoids.…”