Banerjee D, Bernhard J, Burtsev V E, Chumakov A G, Cooke D, Crivelli P, Depero E, Dermenev A V, Donskov S V, Dusaev R R, Enik T, Charitonidis N, Feshchenko A, Frolov V N, Gardikiotis A, Gerassimov S G, Gninenko S N, Hösgen M, Jeckel M, Kachanov V A, Karneyeu A E, Kekelidze G, Ketzer B, Kirpichnikov D V, Kirsanov M M, Kolosov V N, Konorov I V, Kovalenko S G, Kramarenko V A, Kravchuk L V, Krasnikov N V, Kuleshov S V, Lyubovitskij V E, Lysan V, Matveev V A, Mikhailov Yu V, Molina Bueno L, Peshekhonov D V, Polyakov V A, Radics B, Rojas R, Rubbia A, Samoylenko V D, Sieber H, Shchukin D, Tikhomirov V O, Tlisova I, Tlisov D A, Toropin A N, Trifonov A Yu, Vasilishin B I, Vasquez Arenas G, Volkov P V, Volkov V Yu, Ulloa P
CERN, European Organization for Nuclear Research, CH-1211 Geneva, Switzerland.
University of Illinois at Urbana Champaign, Urbana, Illinois 61801-3080, USA.
Phys Rev Lett. 2020 Aug 21;125(8):081801. doi: 10.1103/PhysRevLett.125.081801.
We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10^{11} electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV.
我们利用欧洲核子研究中心（CERN）的高能超级质子同步加速器（SPS）H4电子束，对与两个光子耦合的轻标量粒子和类轴矢赝标量粒子进行了与模型无关的搜索。如果存在新粒子，它们可能通过普里马科夫效应在NA64有源靶中由100 GeV电子产生的硬轫致辐射光子与靶核提供的虚光子的相互作用中产生。轴矢（标量）粒子将穿透作为屏蔽的下游强子量能器（HCAL）模块，并将通过它们在HCAL探测器其余部分的轴矢（标量）→γγ衰变进行观测，或者如果轴矢（标量）粒子在HCAL下游衰变，则作为具有大量缺失能量的事件进行观测。这种方法允许探测轴矢（标量）粒子的参数空间，包括先前实验无法触及的一般轴子模型的参数空间。通过对与靶上2.84×10¹¹个电子对应的数据分析，未发现此类过程的证据，这使我们能够对质量低于55 MeV的轴矢（标量）粒子的γγ耦合强度设定新的限制。
