# NA61 experiment

NA61/SHINE (standing for "SPS Heavy Ion and Neutrino Experiment") is a particle physics experiment at the Super Proton Synchrotron (SPS) at the European Organization for Nuclear Research (CERN). The experiment studies the hadronic final states produced in interactions of various beam particles (pions, protons and beryllium, argon, and xenon nuclei) with a variety of fixed nuclear targets at the SPS energies.
About 135 physicists from 14 countries and 35 institutions work in NA61/SHINE, led by Marek Gazdzicki. NA61/SHINE is the second largest fixed target experiment at CERN.

## Physics program

The NA61/SHINE physics program has been designed to measure hadron production in three different types of collisions:
* In nucleus–nucleus (heavy ion) collisions, in particular the measurement of fluctuations and long range correlations, with the aim to identify the properties of the onset of deconfinement and find evidence for the critical point of strongly interacting matter.
* In proton–proton and proton–nucleus interactions needed as reference data for better understanding of nucleus–nucleus reactions; in particular with regards to correlations, fluctuations and high transverse momenta.
* In hadron–nucleus interactions needed for neutrino (T2K, NOvA and future DUNE) and cosmic-ray experiments (Pierre Auger Observatory and KASCADE).

## Detector

The NA61/SHINE experiment uses a large acceptance hadron spectrometer located on the H2 beam line in the North Area of CERN. It consist of components used by the heavy ion NA49 experiment as well as those designed and constructed for NA61/SHINE.
The main tracking devices are four large volume time projection chambers (TPCs), which are capable of detecting up to 70% of all charged particles created in the studied reactions. Two of them are located in the magnetic field of two super-conducting dipole magnets with maximum bending powers of 9 Tesla meters. Two others are positioned downstream of the magnets symmetrically with respect to the beam line. Additionally, four small volume TPCs placed directly along the beamline region are used in case of hadron and light ion beams.
The setup is supplemented by time of flight detector walls, which extend particle identification to low momenta (1 GeV/c < p ). Furthermore, the Projectile Spectator Detector (a calorimeter) is positioned downstream of the time of flight detectors to measure energy of projectile fragments.

## Collected data

| Type of interaction | Beam momentum $\left({\frac {GeV}{c}}\right)$ | Year | Citation |
| π + Be | 120 | 2016 | CERN-SPSC-2017-038 |
| π + C | 30, 60, 158, and 350 | 2009, 2012, 2016, and 2017 | CERN-SPSC-2016-038, PR D100 112004, and PR D100 112001 |
| π + Al | 60 | 2017 | CERN-SPSC-2016-038 and PR D98 052001 |
| Kaon + C | 158 | 2012 | CERN-SPSC-2016-038 and MPL A34 1950078 |
| p + p | 13, 20, 31, 40, 80, 158, and 400 | 2009, 2010, 2011, and 2016 | EPJ C80 460, SQM 2019 315, and EPJ C74 2794 |
| p + Be | 60, and 120 | 2016 and 2017 | CERN-SPSC-2017-038, and PR D100 112001 |
| p + C p + (T2K replica target) p + (NOvA replica target) | 31, 60, 90, and 120 | 2007, 2009, 2010, 2012, 2016, 2017, and 2018 | CERN-SPSC-2017-038, CERN-SPSC-2016-038, CERN-SPSC-2019-041, PR D100 112001 and EPJ C76 617 |
| p + Al | 60 | 2016 | CERN-SPSC-2017-038 and NP B732 1 |
| p + Pb | 30, 40, 80 and 158 | 2012, 2014, 2016, and 2017 | CERN-SPSC-2015-036 |
| Be + Be | 13A, 19A, 30A, 40A, 75A, and 150A | 2011, 2012, and 2013 | CERN-SPSC-2013-028, PoS 364 305, and EPJ C80 961 |
| C + C and C + CH$_{2}$ | 13A | 2018 | CERN-SPSC-2019-041 |
| Ar + Sc | 13A, 19A, 30A, 40A, 75A and 150A | 2015 | CERN-SPSC-2015-036, PoS 364 305, Acta Phys. Pol. B Proc. Suppl. 10 645 and EPJ C81 397 |
| Xe + La | 13A, 19A, 30A, 40A, 75A, and 150A | 2017 | CERN-SPSC-2018-029 and PoS 364 305 |
| Pb + Pb | 13A, 30A, and 150A | 2016 and 2018 | CERN-SPSC-2016-038, J. Phys. Conf. Ser. 1690 012127 and PR C77 064908 |

## Extended program: after Long Shutdown 2

In 2018 the NA61/SHINE collaboration published an addendum presenting an intent to upgrade the experimental facility and perform a new set of measurements after Long Shutdown 2. As in the original program, the new one proposes studies of hadron-nucleus and nucleus-nucleus interactions for heavy ions, neutrino and cosmic-ray physics.
The heavy ions program will focus on study of charm hadron production (mostly D mesons) in lead-lead interactions.
In 2020 the SPS and PS Experiments Committee (SPSC) recommended approval of beam time in 2021. The Research Board endorsed these recommendations.