TrappedIons.org

V. Togo

MoEDAL search in the CMS beam pipe for magnetic monopoles produced via the Schwinger effect

B. Acharya [1], J. Alexandre [1,2], S. C. Behera, P. Benes [3], B. Bergmann [3], S. Bertolucci [4], A. Bevan [5], R. Brancaccio [6], H. Branzas [7], P. Burian [3], M. Campbell [8], S. Cecchini [4], Y. M. Cho [9], M. de Montigny [10], A. De Roeck [8], J. R. Ellis [1,11], M. Fairbairn [1], D. Felea [7], M. Frank [12], O. Gould [13], J. Hays [5,14], A. M. Hirt, D. L. -J. Ho [15], P. Q. Hung [16], J. Janecek [3], M. Kalliokoski [17,8], D. H. Lacarrere, C. Leroy [18], G. Levi [6], A. Margiotta [6], R. Maselek [19], A. Maulik [4,10], N. Mauri [6], N. E. Mavromatos [1], L. Millward [5], V. A. Mitsou [20], E. Musumeci [20], I. Ostrovskiy [2], P. -P. Ouimet [21], J. Papavassiliou [20], L. Patrizii [4,7], G. E. Pavalas, J. L. Pinfold [10], L. A. Popa [7], V. Popa [7], M. Pozzato [4], S. Pospisil [3], A. Rajantie [15], R. Ruiz de Austri [20], Z. Sahnoun [6], M. Sakellariadou [1], K. Sakurai [19], S. Sarkar [1], G. Semenoff [22], A. Shaa [10], G. Sirri [4], K. Sliwa [23], R. Soluk [10], M. Spurio [6], M. Staelens [20], M. Suk [3], M. Tenti [4], V. Togo [4,10], J. A. Tuszynski, A. Upreti [2], V. Vento [20], O. Vives [20]

Abstract

We report on a search for magnetic monopoles (MMs) produced in ultraperipheral Pb--Pb collisions during Run-1 of the LHC. The beam pipe surrounding the interaction region of the CMS experiment was exposed to 184.07 \textmu b$^{-1}$ of Pb--Pb collisions at 2.76 TeV center-of-mass energy per collision in December 2011, before being removed in 2013. It was scanned by the MoEDAL experiment using a SQUID magnetometer to search for trapped MMs. No MM signal was observed. The two distinctive features of this search are the use of a trapping volume very close to the collision point and ultra-high magnetic fields generated during the heavy-ion run that could produce MMs via the Schwinger effect. These two advantages allowed setting the first reliable, world-leading mass limits on MMs with high magnetic charge. In particular, the established limits are the strongest available in the range between 2 and 45 Dirac units, excluding MMs with masses of up to 80 GeV at 95\% confidence level.

First experimental search for production of magnetic monopoles via the Schwinger mechanism

B. Acharya [1], J. Alexandre [1], P. Benes [2], B. Bergmann [2], S. Bertolucci [3], A. Bevan [4], H. Branzas [5], P. Burian [2], M. Campbell [6], Y. M. Cho [7], M. de Montigny [8], A. De Roeck [6], J. R. Ellis [1,9], M. El Sawy [6], M. Fairbairn [1], D. Felea [5], M. Frank [10], O. Gould [11,12], J. Hays [4], A. M. Hirt [13], D. L. J. Ho [14], P. Q. Hung [15], J. Janecek [2], M. Kalliokoski [16], A. Korzenev [17,6], D. H. Lacarrère, C. Leroy [18], G. Levi [19], A. Lionti [17], A. Maulik [3,8], A. Margiotta [19], N. Mauri [3], N. E. Mavromatos [1,20], P. Mermod [17,4], L. Millward, V. A. Mitsou [21], I. Ostrovskiy [22], P. -P. Ouimet [8], J. Papavassiliou [21], B. Parker [23], L. Patrizii [3,5], G. E. Păvălaş, J. L. Pinfold [8], L. A. Popa [5], V. Popa [5], M. Pozzato [3], S. Pospisil [2], A. Rajantie [14], R. Ruiz de Austri [21], Z. Sahnoun [3], M. Sakellariadou [1], A. Santra [21], S. Sarkar [1], G. Semenoff [24], A. Shaa [8], G. Sirri [3], K. Sliwa [25], R. Soluk [8], M. Spurio [19], M. Staelens [8], M. Suk [2], M. Tenti [26], V. Togo [3,8], J. A. Tuszyński, A. Upreti [22], V. Vento [21], O. Vives [21]

Abstract

Schwinger showed that electrically-charged particles can be produced in a strong electric field by quantum tunnelling through the Coulomb barrier. By electromagnetic duality, if magnetic monopoles (MMs) exist, they would be produced by the same mechanism in a sufficiently strong magnetic field. Unique advantages of the Schwinger mechanism are that its rate can be calculated using semiclassical techniques without relying on perturbation theory, and the finite MM size and strong MM-photon coupling are expected to enhance their production. Pb-Pb heavy-ion collisions at the LHC produce the strongest known magnetic fields in the current Universe, and this article presents the first search for MM production by the Schwinger mechanism. It was conducted by the MoEDAL experiment during the 5.02 TeV/nucleon heavy-ion run at the LHC in November 2018, during which the MoEDAL trapping detectors (MMTs) were exposed to 0.235 nb$^{-1}$ of Pb-Pb collisions. The MMTs were scanned for the presence of magnetic charge using a SQUID magnetometer. MMs with Dirac charges 1$g_D$ $\leq$ $g$ $\leq$ 3$g_D$ and masses up to 75 GeV/c$^2$ were excluded by the analysis. This provides the first lower mass limit for finite-size MMs from a collider search and significantly extends previous mass bounds.