CERN Accelerating science

Scientific Committee Paper
Report number	CERN-LHCC-2024-011 ; LHCC-I-041
Title	ALADDIN: An Lhc Apparatus for Direct Dipole moments INvestigation
Project Manager/Technical Coordinator	Neri, Nicola; Martinez Vidal, Fernando
Author(s)	Akiba, K ; Alessio, F ; Benettoni, M ; Bizzeti, M ; Borgato, F ; Bucci, F ; Cardinale, R ; Cesare, S ; Citterio, M ; Coco, V ; Collins, P ; Dall’Occo, E ; Ferro-Luzzi, M ; Fomin, A ; Forty, R ; Fu, J ; Gandini, P ; Giorgi, M ; Grabowski, J ; Jaimes Elles, S J ; Jakobsen, S ; Kou, E ; Lamanna, G ; Li, H ; Libralon, S ; Marangotto, D ; Martinez Vidal, F ; Mazorra de Cos, J ; Merli, A ; Miao, H ; Neri, N ; Neubert, S ; Petrolini, A ; Pilloni, A ; Pinzino, J ; Prest, M ; Robbe, P ; Rossi, L ; Ruiz-Vidal, J ; Sanderswood, I ; Sergi, A ; Simi, G ; Sorbi, M ; Sozzi, M ; Spadaro Norella, E ; Stocchi, A ; Tonani, G ; Tork, T ; Triossi, A ; Turini, N ; Vallazza, E ; Vico Gil, S ; Wang, Z ; Wang, M ; Xing, T ; Zanetti, M ; Zangari, F
Corporate author(s)	CERN. Geneva. The LHC experiments Committee ; LHCC
Series	(Letter of Intent)
DOI	10.17181/CERN.2G4V.0YAO
Submitted by	nicola.neri@cern.ch on 24 Jul 2024
Referee	nicola.neri@cern.ch on 24 Jul 2024
Subject category	Detectors and Experimental Techniques
Abstract	Magnetic and electric dipole moments of composite or fundamental particles provide powerful probes for physics within and beyond the Standard Model. For the case of short-lived charm baryons, these properties have not been experimentally accessible to date due to the difficulties imposed by their short lifetimes. In this Letter of Intent, a small fixed-target experiment at the LHC is proposed, ALADDIN, which will enable a unique program of measurements of charm baryon electromagnetic dipole moments. The experiment relies on an innovative storage-ring layout capable of deflecting protons from the beam halo towards a solid target paired to a bent crystal where forward-boosted charm baryons are produced and channelled. Exploiting the spin precession induced by the channelling phenomena in the bent crystal, the magnetic and electric dipole moments can be measured by analysing the polarisation of the decaying charm baryons. According to simulation studies, a significant measurement of dipole moments is possible after two years of data taking. A proof-of-principle test at the LHC, named TWOCRYST, is currently under way to demonstrate the feasibility of the proposed experiment in 2025. The ALADDIN apparatus features a 4.4 m long spectrometer and a 5.0 m long RICH detector for particle identification, which could be installed at the LHC Insertion Region 3, without civil engineering and with minimal impact on the LHC machine operations, aiming at data taking within Run 4. The ALADDIN physics program, detector layout, location and machine aspects are described, along with the simulation results and the experimental conditions. A preliminary estimate of the experiment cost, funding and timeline is also provided.

Email contact(s) : nicola.neri@mi.infn.it ; fernando.martinez@ific.uv.es