Search for a New Gauge Boson in Electron-Nucleus Fixed-Target Scattering by the APEX Experiment

We investigate the LHC signals of a minimal supersymmetric hidden valley. Our theory consists of the supersymmetric Standard Model along with a light hidden U (1) x gauge multiplet and a pair of hidden chiral superfields that spontaneously break the new Abelian gauge symmetry near a GeV. The visible and hidden sectors interact exclusively through supersymmetric gauge kinetic mixing. We perform a thorough examination of the hidden decay cascades initiated by the lightest Standard Model superpartner and we study the range of LHC signals they can produce. In particular, we find parameter regions that give rise to missing energy, single and multiple lepton jets, and displaced vertices. Given the simplicity of the underlying theory and the broad range of collider signals it can produce, we propose that this model is a useful benchmark for LHC studies of (supersymmetric) hidden valleys.

Section: Hidden Sector Parameter Scansupporting

confidence: 49%

LHC signatures of a minimal supersymmetric hidden valley

Chan

Low

Morrissey

et al. 2012

“…In both panels, the "Short-Lived" region indicates that the DM lifetime is shorter than the age of Universe. Assuming m γ d mγ d , additional constraints exist from beam-dump [82,83], fixedtarget [84,85], and colliding-beam experiments [86]; precision measurements [87]; stars [88,89]; and from the intergalactic diffuse photon background (IDPB). This final constraint is valid for hidden photons below 2m e 1 MeV, as these can decay to three photons and contribute to the diffuse photon background [34,90].…”

Section: Hidden Photinomentioning

confidence: 99%

Constraining light dark matter with diffuse X-ray and gamma-ray observations

Essig

Kuflik

McDermott

et al. 2013

315

431

We present constraints on decaying and annihilating dark matter (DM) in the 4 keV to 10 GeV mass range, using published results from the satellites HEAO-1, INTEGRAL, COMPTEL, EGRET, and the Fermi Gamma-ray Space Telescope. We derive analytic expressions for the gamma-ray spectra from various DM decay modes, and find lifetime constraints in the range 10 24 − 10 28 sec, depending on the DM mass and decay mode. We map these constraints onto the parameter space for a variety of models, including a hidden photino that is part of a kinetically mixed hidden sector, a gravitino with Rparity violating decays, a sterile neutrino, DM with a dipole moment, and a dark pion. The indirect constraints on sterile-neutrino and hidden-photino DM are found to be more powerful than other experimental or astrophysical probes in some parts of parameter space. While our focus is on decaying DM, we also present constraints on DM annihilation to electron-positron pairs. We find that if the annihilation is p-wave suppressed, the galactic diffuse constraints are, depending on the DM mass and velocity at recombination, more powerful than the constraints from the Cosmic Microwave Background.

“…[60]. Shown are existing 90% CL exclusion regions from beam dump experiments E137, E141, and E774 [16][17][18], Orsay [23], U70 [24], CHARM [25], LSND [26], A1 [20], the electron and muon anomalous magnetic moment [33][34][35], HADES [30], KLOE [28,29], the test run results reported by APEX [19], an estimate using a BaBar result [22,31,32], and constraints from astrophysical observations [36,37] JHEP11 (2014) -31 -…”

Section: Frvz Model Excluded Cτ [Mm]mentioning

confidence: 99%

“…Related searches for prompt LJs have been performed both at the Tevatron [10,11] and at the LHC [12][13][14][15]. Additional constraints on scenarios with hidden photons are extracted from, e.g., beam-dump and fixed-target experiments [16,17,[17][18][19][20][21][22][23][24][25][26][27], e + e − colliders [28][29][30], B-factories [31,32], electron and muon anomalous magnetic moment measurements [33][34][35] and astrophysical observations [36,37].The properties of the LJ, such as its shape and particle multiplicity, strongly depend on the unknown structure of the hidden sector and its couplings to the visible sector. Therefore the search criteria must be as model-independent as possible, targeting the basic experimental signatures that correspond to these objects.…”

mentioning

confidence: 99%

Search for long-lived neutral particles decaying into lepton jets in proton-proton collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

Aad¹,

Abbott²,

Abdallah³

et al. 2014

Self Cite

109

Several models of physics beyond the Standard Model predict neutral particles that decay into final states consisting of collimated jets of light leptons and hadrons (socalled "lepton jets"). These particles can also be long-lived with decay length comparable to, or even larger than, the LHC detectors' linear dimensions. This paper presents the results of a search for lepton jets in proton-proton collisions at the centre-of-mass energy of √ s = 8 TeV in a sample of 20.3 fb −1 collected during 2012 with the ATLAS detector at the LHC. Limits on models predicting Higgs boson decays to neutral long-lived lepton jets are derived as a function of the particle's proper decay length. An extensively studied case is one in which the two sectors couple via the vector portal, in which a light hidden photon (dark photon, γ d ) mixes kinetically with the SM photon. If the hidden photon is the lightest state in the hidden sector, it decays back to SM particles with branching fractions that depend on its mass [6,8,9]. For the case in which the γ d kinetically mixes with hypercharge, one finds that , the kinetic mixing parameter, controls -1 - Keywords: Hadron-Hadron Scattering JHEP11(2014)088both the γ d decay branching fractions and lifetime. More generally, however, the branching fractions and lifetime are model-dependent and may depend on additional parameters.Due to their small mass, these particles are typically produced with a large boost and, due to their weak interactions, can have non-negligible lifetime. As a result one may expect, from dark photon decays, collimated jet-like structures containing pairs of electrons and/or muons and/or charged pions ("lepton jets", LJs) that can be produced far from the primary interaction vertex of the event (displaced LJs).Neutral particles which decay far from the interaction point into collimated final states represent a challenge both for the trigger and for the reconstruction capabilities of the LHC detectors. Collimated charged particles in the final state can be difficult to disentangle due to the limited granularity of the detector. Moreover, in the absence of information from the inner tracking system, it is necessary to use the muon spectrometer (MS) for the reconstruction of tracks which originate from a secondary decay far from the primary interaction vertex (IP).The high-resolution, high-granularity measurement capability of the ATLAS "air-core" MS is ideal for this type of search. In addition, the ATLAS inner tracking system can be used to define isolation criteria to significantly reduce, for decay vertices far from the interaction point, the otherwise overwhelming SM background from proton-proton collisions.The search for displaced LJs presented in this paper employs the full dataset collected by ATLAS during the 2012 run at √ s = 8 TeV, corresponding to an integrated luminosity of 20.3 fb −1 . Related searches for prompt LJs have been performed both at the Tevatron [10,11] and at the LHC [12][13][14][15]. Additional constraints on scenarios with hidden phot...