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Pos(LHCP2019)182 ∗† Jurgen.Engelfried@Cern.Ch Speaker Dark sector searches in non-LHC experiments PoS(LHCP2019)182 Jürgen Engelfried∗y Instituto de Física, Universidad Autónoma de San Luis Potosí, Mexico E-mail: [email protected] We will present recently published and soon to be expected results for dark matter searches in non-LHC experiments, namely BABAR, NA62, NA64, BELLE II, and PADME. 7th Annual Conference on Large Hadron Collider Physics - LHCP2019 20-25 May, 2019 Puebla, Mexico ∗Speaker. yThanks to the organizers for the invitation to give this presentation. c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). https://pos.sissa.it/ Dark sector searches in non-LHC experiments Jürgen Engelfried 1. Introduction The need for an extension of the Standard Model (SM) – the dark sector – is well known and will not be discussed here. Introducing new particles and interactions depend on the type of fields used, and are usually separated into Scalars (also called “dark Higgs”), Axial particles called “Axions” and ALP’s (Axion like particles), and new Vector Interactions, with a new vector boson called the “Dark Photon”. Other possible candidates for dark sector particles are heavy neutral leptons (heavy neutrinos), and some other solutions. In this presentation we will present recent already public results and expectations from non- PoS(LHCP2019)182 LHC experiments which are already running or will start in the near future, namely from BABAR, NA62, NA64, Belle II, and PADME. 2. Dark Photons A simple and natural extension of the SM is the introduction of a new interaction with a U(1) symmetry [1,2], with the new boson, the “dark photon” A0, interacting with the SM sector through a kinetic mixing e QED mn Lmix = F F −2 mn dark where e is the kinetic mixing strength. The smaller e the longer is the lifetime of the A0. If the A0 is the lightest “Dark Sector” particle, it can only decay to SM particles, otherwise it can also decay in (lighter) dark sector particles. For the experimental signatures and searches we have to distinguish two main cases: 1) The A0 is the lightest “dark” particle and has a sufficiently short lifetime to decay into SM particles within the experimental setup, and 2) The A0 is very long lived and/or decays into dark particles only and the experimental signature would be missing energy/momentum. For both cases there are recent experimental results which will be presented in the following. 2.1 BABAR: e+e gA , A e+e ; m+m − ! 0 0 ! − − The seminal study of BABAR in 2014 [3] searches for a short-lived A0 produced together with m a photon, decaying into a pair of electrons or muons. No signal is observed, and limits in the e- A0 3 c2 m c2 plane are (see fig. 1 left): e . 10− for 0:02GeV= . A0 . 10:2GeV= 2.2 NA64: e Z e ZA , A e+e − ! − 0 0 ! − A more recent search by NA64, a fixed target experiment at CERN with a 100GeV=c e− beam, M A e+e probing lower A0 masses and also smaller e, looks for 0 − [4], with special emphasis for 2 ! 8 A0 = X with mX = 16:7MeV=c , the a new boson postulate to explain anomalies in Be decays [5]. No signal is observed (see fig. 1 right). 2.3 BABAR: e+e gA , A invisible − ! 0 0 ! In this recent analysis [6] BABAR search for a long-lived A0, with the experimental signature being a single photon and large missing momentum and energy. After observing no signal, the 3 m c2 limits (see fig. 2 left) are e . 10− for a large mass range A0 < 8GeV= . 1 PHYSICAL REVIEW LETTERS week ending PRL 113, 201801 (2014) 14 NOVEMBER 2014 e+e- μ+μ- ) fb - e + 50 102 102 e → 0 10 10 Entries Entries A’, A’ γ → - e -50 1 1 + (e σ -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 4 SS SS 2 S S 0 -2 FIG. 3 (color online). Distribution of the statistical significance -4 (SS) from the fits to the dielectron (left) and dimuon (right) final 0246810 states, together with the expected distribution for the null m (GeV) A’ hypothesis (dashed line). ) fb 10 - μ + section, assuming a flat prior for the cross section. The μ limits are typically at the level of Oð1–10Þ fb. These results → are finally translated into 90% C.L. upper limits on the 0 A’, A’ mixing strength between the photon and dark photon as a γ → function of the dark photon mass [10]. The results are - e + displayed in Fig. 4. The average correlation between (e -10 σ neighboring points is around 90%. Bounds at the level −4 −3 4 of 10 –10 for 0.02 <mA0 < 10.2 GeV are set,PHYSICAL signifi- REVIEW LETTERS 120, 231802 (2018) 2 0 S 0 cantly improving previous constraintsTABLE I. Expected derived numbers from of background beam- events in the normalization, A yield, and decay probability, which were S 5 4 1010 0 -2 signal box estimated for . × EOT. the A mass dependent, and also from efficiencies and dump experiments [11,12,18], theweek electron ending anomalous their uncertainties in the primary e−ð0.85Æ0.02Þ, -4 PRL 119, 131804 (2017) PHYSICAL REVIEW LETTERS Source29 of SEPTEMBER background 2017 Events magnetic moment [13], KLOE [14,15], WASA-at-COSY WCALð0.93Æ0.05Þ, V2ð0.96Æ0.03Þ,ECALð0.93Æ0.05Þ, 0246810 þ − γ 0 001 ð0 95 Æ 0 04Þ ð0 98 Æ 0 02Þ −6 e e pair production by punchthrough < . V3 . , and HCAL . event detection. ×10 0 → 2π0 π0 → γ þ − γ → þ − 0 → πþπ− 0.06 Æ 0.034 mA’ (GeV) [16], HADES3 [17], A1 at MAMIKS [19]; , ande e ; thee teste ; KS run from The latter, shown as example values for the 40 X0 run, were 3 πN → ð≥ 1Þπ0 þ n þÁÁÁ; π0 → γeþe−; γ → eþe− 0.01 Æ 0.004 determined from measurements with the e− beam cross- APEX [20]. TheseBayesian results limit alsoπ− bremsstrahlung supersede in the WCAL,andγ extend→ eþe− the< 0.0001 checked with simulations. A detailed simulation of the e.m. þ − 0 0 þ − þ − 0 π → ν 0 001 0 2.5 ;K e , Ke4 decays < . shower in the dump [63] with A cross sections was used to FIG. 2. The e e 2.5→ γA , A → e e (top) and e e → γA , Profile-likelihood limit þ − Æ Æ CP ) constraints based on a search for a light -odd Higgs 0 001 0 eZ → eZμ μ ; μ → e νν < . calculate the A yield [64,69,70]. The ≲10% difference 0 þ − σ π 0 003 A → μ μ (bottom) cross sections together with their respective Punchthrough < . between the calculations in Ref. [64] and Refs. [69,70] was boson at2 BABAR [21,22] with a smaller data set. No signal 2 Total 0.07 Æ 0.035 n 0 ðϵ;m 0 Þ statistical significance (SS) as a function of the dark photon mass. accounted for as a systematic uncertainty in A A .In consistent with the excess reported by the HyperCP experi- the overall signal efficiency for each run, the acceptance loss The gray bands indicate1.5 the mass regions that are excluded from 1.5 due to pileup (≃7% for 40 X0 and ≃10% for 30 X0 runs) was ment close to 214 MeV is observeddecay photons escaping[38,39] the dump. We without further interactions and taken into account and cross-checked using reconstructed the analysis. accompanied by poorly detected secondaries, is another dimuon events [57]. The dimuon efficiency corrections Significance ( 1 constrain the range of the parameter space favored by 1 source of fake signal. To evaluate this background we used (≲20%) were obtained with uncertainty of 10% and 15%, Darkinterpretations sector searches of the in non-LHC discrepancythe experiments extrapolation between of the charge-exchangethe calculated cross sections, for the 40 X0 and 30 X0 Jürgenruns, respectively. Engelfried The total Upper Limit at 90% CL 2 3 0.5 2 σ ∼ = systematic uncertainty on N 0 calculated by adding all ε Z , measured on different nuclei [65]. The contribution A 0.5 − − þ − obtained by combining the signal yields of each data and measured anomalous magneticfrom the beam moment kaon decays in of flight, theK → muone νπ π ðKe4Þ, errors in quadrature did not exceed 25% for both runs. 0 and dimuon production in the dump e−Z → e−Zμþμ− with The combined 90% C.L. exclusion limits on the mixing ϵ as 012345678 þ − þ − 0 sample divided by the efficiency and luminosity. The cross 0 either π π or μ μ pairs misidentified as e.m. event in the a function of the A mass is shown in Fig. 3 together with the mA' (GeV) 012345678 sections as a function of mA0 are shown in Fig. 2; the -2 m (GeV)ECAL was found to be negligible. current constraints from other experiments. Our results 10 A' Table I summarizes the conservatively estimated back- exclude the X boson as an explanation for the 8Be anomaly KLOE 2013 − −4 distributionsFIG. of the 2. statisticalSignal significance significancesS as a function of of the the fits mass arem 0 . ground inside the signal box, which is expected to be for the X − e coupling ϵe ≲ 4.2 × 10 and mass value of A 0 BABAR 10 FIG. 4. Upper limits at 90% C.L. on A0.mixing07 Æ 0.034 strengthevents persquared20095.4 × 10 EOT.
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