# SND Experiment

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/SND_Experiment
> Markdown URL: https://mediated.wiki/source/SND_Experiment.md
> Source: https://en.wikipedia.org/wiki/SND_Experiment
> Source revision: 1313376057
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

**Spherical Neutral Detector** ([**SND**](http://wwwsnd.inp.nsk.su/)) is a [detector](/source/Detector) for [particle physics](/source/Particle_physics) [experiments](/source/Experiment), successor of the [Neutral Detector](/source/ND_Experiment) ([ND](/source/ND_Experiment)),[1] created by the team of physicists in the [Budker Institute of Nuclear Physics](/source/Budker_Institute_of_Nuclear_Physics) [(BINP)](http://www.inp.nsk.su/index.en.shtml) [Archived](https://web.archive.org/web/20060207105713/http://www.inp.nsk.su/index.en.shtml) 2006-02-07 at the Wayback Machine, [Novosibirsk](/source/Novosibirsk), [Russia](/source/Russia). There are three major periods in evolution of the **SND** experiment;

- from 1995 to 2000 - data collection at the e+e− [storage ring](/source/Storage_ring) [VEPP-2M](http://www.inp.nsk.su/activity/old/vepp2m/index.ru.shtml) in the [energy](/source/Energy) range 2E=0.4-1.4 GeV,
- from 2001 to 2008 - [upgrade of SND](https://arxiv.org/abs/hep-ex/0105093)[2] and the [storage ring](/source/Storage_ring) [VEPP-2M](http://www.inp.nsk.su/activity/old/vepp2m/index.ru.shtml) to [VEPP-2000](/source/VEPP-2000),
- from 2009 - data collection at the e+e− [storage ring](/source/Storage_ring) [VEPP-2000](http://vepp2k.inp.nsk.su/) in the [energy](/source/Energy) range 2E=1.0-2.0 GeV.

## Physics

Previous experiment with [ND](/source/ND_Experiment)[3] (predecessor of **SND**) has shown that the e+e− annihilation in the final states with neutral particles in the energy range 2E=0.4-1.4 GeV is mediated by the processes which need to be studied in more details. In particular,

- quark structure of the light scalar mesons can be studied in electric-dipole radiative decays \phi \to a_0(980) \gamma, ~~ f_0(975) \gamma;
- precise measurement of the e+e−[annihilation](/source/Annihilation) cross section into [hadrons](/source/Hadron) is the important component in definition of the muon [anomalous magnetic dipole moment](/source/Anomalous_magnetic_dipole_moment);[4]
- precise measurement of the hadronic cross sections is necessary to study the radial excitation of the light vector mesons ρ, ω, and φ;
- measurement of the higher order [quantum electrodynamic](/source/Quantum_electrodynamics) (QED]) processes is important for the QED theory test.

This physics can be studied with dedicated detector at higher statistics. For this purpose the **SND** was constructed with many improvements relative to [ND](/source/ND_Experiment);

- the solid angle is covered up to 96% of 4π sr,
- the [NaI](/source/NaI)(Tl) [calorimeter](/source/Calorimeter_(particle_physics)) has uniform spherical shape with fine segmentation in azimuthal and polar angles and 3 layers in radial direction,
- drift chamber is used as a central tracker,
- external anti-coincidence flat scintillation counters are enhanced by the coordinate system made of arrays of strimmer tubes.

## Experimental program

Experimental program of the **SND** is presented in Ref.[5] and consists of items as follow.

- [Radiative decays](/source/Particle_decay)

- e^+e^- \to \rho, \omega, \phi \to \pi^0 \gamma, \eta \gamma
- \phi \to \eta^\prime \gamma
- \phi \to a_0(980) \gamma, ~~ f_0(975) \gamma, ~~ \pi \pi \gamma, ~~ \eta \pi \gamma
- \rho, \omega \to \pi \pi \gamma

- [OZI](/source/OZI_Rule) and [G-parity](/source/G-parity) suppressed decays

- \phi \to \omega \pi^0, ~~ \pi \pi, ~~ \eta \pi \pi
- \rho \to \pi^+ \pi^- \pi^0
- \omega \to \pi^+ \pi^-

- Electromagnetic decays

- \rho, \omega, \phi \to \eta e^+e^-, ~~ \pi^0 e^+e^-

- e+e− [annihilation](/source/Annihilation) into [hadrons](/source/Hadron)

- e^+e^- \to 2\pi,~~ 3\pi,~~ 4\pi,~~ 5\pi
- e^+e^- \to \omega \pi,~~ \eta \pi \pi,~~ \phi \pi
- e^+e^- \to K^+ K^-,~~ K^0_S K^0_L ,~~ K K \pi

- Test of [QED](/source/Quantum_electrodynamics) processes

- e^+e^- \to 3\gamma , ~~ e^+e^- \gamma
- e^+e^- \to 4 \gamma, ~~ e^+e^- \gamma \gamma , ~~ e^+e^- e^+e^-
- e^+e^- \to 5\gamma, ~~ 3\gamma e^+e^-, ~~ 4e\gamma

- Search for rare decays

- K^0_S \to \gamma \gamma, ~~ 3\pi^0, ~~ 2\pi^0 \gamma, ~~ \pi^0 \gamma \gamma, ~~ \pi^0 e^+e^-
- \eta \to 3\gamma, ~~ e^+e^-, ~~ 4e

- Search for [C-even](/source/C-parity) reactions

- e^+e^- \to \eta^\prime,~~ a_0,~~ f_0,~~ a_2,~~ f_2

## Detector

The **SND** and its upgraded version are described in Refs.[5] and,[2] respectively. The detector design is illustrated in the [R-θ view](http://wwwsnd.inp.nsk.su/SND_Icons/sndcut1.gif) and [3-D plot of the NaI(Tl) calorimeter segmentation](http://wwwsnd.inp.nsk.su/SND_Icons/sndball.gif). Unique features of the **SND** and its sensitivity to the neutral particles are defined by the state-of-art NaI(Tl) calorimeter.

## Results

[Data](/source/Data) collected in the **SND** experiment from 1995 to 2000 corresponds to the integrated [luminosity](/source/Luminosity) 30 pb−1 spread in the energy range 2E=0.4-1.4 GeV. Review of results of this experiment is presented in Refs. [6] and .[7] Results are included in the [PDG](/source/Particle_Data_Group) Review.[8] Complete [list of publications from **SND**](http://wwwsnd.inp.nsk.su/SND_Publications/) also covers recent results of the experiment in the energy range 2E=1.0-2.0 GeV started in 2009.

## References

1. Golubev, V. B. et al. (1984). "The neutral detector at VEPP-2M". *Nuclear Instruments and Methods in Physics Research Section A*. **227** (3): 467–469. [Bibcode:1984NIMPA.227..467G](https://ui.adsabs.harvard.edu/abs/1984NIMPA.227..467G). [doi:10.1016/0168-9002(84)90202-X](https://doi.org/10.1016/0168-9002(84)90202-X)

1. Abramov, G. N. et al. (2001). "SND Upgrade". *Invited talk at the e+e− Physics at Intermediate Energies Workshop, SLAC, Stanford, California, April 30 - May 2*. Vol. 675. pp. 391–397. [Bibcode:2001eepi.conf..122D](https://ui.adsabs.harvard.edu/abs/2001eepi.conf..122D)

1. Dolinsky, S. I. et al. (1991). "Summary of experiments with the neutral detector at the e+e− storage ring VEPP-2M". *Physics Reports*. **202** (3): 99–170. [Bibcode:1991PhR...202...99D](https://ui.adsabs.harvard.edu/abs/1991PhR...202...99D). [doi:10.1016/0370-1573(91)90127-8](https://doi.org/10.1016/0370-1573(91)90127-8)

1. (g-2) Design Report, BNL, 1995.

1. V. M. Aulchenko *et al.*, "Beginning of the Experiments with SND Detector at e+e− Collider VEPP-2M", preprint [BINP 95-56](http://www.inp.nsk.su/activity/preprints/oldwww/inp95_56/text.ps) (1995); Proceedings of the 6th International Conference on Hadron Spectroscopy (HADRON 95), Manchester, England, 10-14 Jul 1995, p.295-297.

1. Achasov, M. N. et al. (2002). "Review of experimental results from SND detector". *AIP Conf. Proc.*. **619**: 30–39. [arXiv:hep-ex/0109035](https://arxiv.org/abs/hep-ex/0109035). [doi:10.1063/1.1482433](https://doi.org/10.1063/1.1482433). [S2CID 204924486](https://api.semanticscholar.org/CorpusID:204924486)

1. Achasov, M. N. et al. (2000). "New Data from SND Detector in Novosibirsk". *Nucl. Phys. A*. **675** (1–2): 391–397. [arXiv:hep-ex/9910057](https://arxiv.org/abs/hep-ex/9910057). [Bibcode:2000NuPhA.675..391A](https://ui.adsabs.harvard.edu/abs/2000NuPhA.675..391A). [doi:10.1016/S0375-9474(00)00295-5](https://doi.org/10.1016/S0375-9474(00)00295-5). [S2CID 16033410](https://api.semanticscholar.org/CorpusID:16033410)

1. [The Review of Particle Physics](http://pdg.lbl.gov/index.html), [K. Nakamura et al. (Particle Data Group), J. Phys. G 37, 075021 (2010)](http://iopscience.iop.org/0954-3899/37/7A/075021)

## External links

[SND experiment](https://inspirehep.net/experiments/1109026) record on [INSPIRE-HEP](/source/INSPIRE-HEP)

## See also

- [ND experiment](/source/ND_experiment)
- [Budker Institute of Nuclear Physics](/source/Budker_Institute_of_Nuclear_Physics)
- [Particle detector](/source/Particle_detector)

---
Adapted from the Wikipedia article [SND Experiment](https://en.wikipedia.org/wiki/SND_Experiment) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/SND_Experiment?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.