LIMITS ON NEUTRAL PARTICLE PRODUCTION

Heavy Particle Production Cross Section

INSPIRE   PDGID:
S015CS
VALUE (cm${}^{2}/{{\mathit N}}$) CL% DOCUMENT ID TECN  COMMENT
• • We do not use the following data for averages, fits, limits, etc. • •
1
TUMASYAN
2022AG
 CMS SIMP search
2
AAD
2021F
 ATLS monojet search
3
AAIJ
2020AL
 LHCB ${{\mathit p}}{{\mathit p}}$ at 13 TeV, dimuon resonance
4
SIRUNYAN
2020AY
 CMS ${{\mathit \Upsilon}{(1S)}}{{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ decay states
5
SIRUNYAN
2020Z
 CMS multilepton BSM search, 13 TeV
6
AABOUD
2019H
 ATLS di-photon-jet resonance
7
AABOUD
2019V
 ATLS review, mediator-based DM
8
SIRUNYAN
2019O
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \gamma}}$ $\not E_T$
9
AABOUD
2018CJ
 ATLS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit V}}{{\mathit V}}$ $/$ ${{\mathit \ell}}{{\mathit \ell}}$ $/$ ${{\mathit \ell}}{{\mathit \nu}}$ , ${{\mathit V}}$ = ${{\mathit W}},{{\mathit Z}},{{\mathit h}}$
10
AABOUD
2018CM
 ATLS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit e}}{{\mathit \mu}}$ $/$ ${{\mathit e}}{{\mathit \tau}}$ $/$ ${{\mathit \mu}}{{\mathit \tau}}$
11
AAIJ
2018AJ
 LHCB ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit A}^{\,'}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ ; dark photon
12
BANERJEE
2018
NA64 ${{\mathit e}}$ ${{\mathit Z}}$ $\rightarrow$ ${{\mathit e}}{{\mathit Z}}{{\mathit X}}$( ${{\mathit A}^{\,'}}$)
13
BANERJEE
2018A
 NA64 ${{\mathit e}}$ ${{\mathit Z}}$ $\rightarrow$ ${{\mathit e}}{{\mathit Z}}{{\mathit A}^{\,'}}$ , ${{\mathit A}^{\,'}}$ $\rightarrow$ ${{\mathit \chi}}{{\mathit \chi}}$
14
MARSICANO
2018
E137 ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit A}^{\,'}}$( ${{\mathit \gamma}}$) visible decay
15
SIRUNYAN
2018BB
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit Z}^{\,'}}$ $\rightarrow$ ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ at 13 TeV
16
SIRUNYAN
2018DA
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ Black Hole, string ball, sphaleron
17
SIRUNYAN
2018DD
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit j}}{{\mathit j}}$
18
SIRUNYAN
2018DR
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit b}}{{\mathit \mu}}{{\overline{\mathit \mu}}}$
19
SIRUNYAN
2018DU
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$
20
SIRUNYAN
2018ED
 CMS ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit V}}$ $\rightarrow$ ${{\mathit W}}{{\mathit h}}$ ; ${{\mathit h}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ ; ${{\mathit W}}$ $\rightarrow$ ${{\mathit \ell}}{{\mathit \nu}}$
21
AABOUD
2017B
 ATLS ${{\mathit W}}{{\mathit H}}$ , ${{\mathit Z}}{{\mathit H}}$ resonance
22
AAIJ
2017BR
 LHCB ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \pi}_{{{v}}}}{{\mathit \pi}_{{{v}}}}$ , ${{\mathit \pi}_{{{v}}}}$ $\rightarrow$ ${{\mathit j}}{{\mathit j}}$
23
AAD
2016O
 ATLS ${{\mathit \ell}}$ + (${{\mathit \ell}}$s or jets)
24
AAD
2016R
 ATLS ${{\mathit W}}{{\mathit W}}$ , ${{\mathit W}}{{\mathit Z}}$ , ${{\mathit Z}}{{\mathit Z}}$ resonance
25
KRASZNAHOR..
2016
${{\mathit p}}$ ${}^{7}\mathrm {Li}$ $\rightarrow$ ${}^{8}\mathrm {Be}$ $\rightarrow$ ${{\mathit X}{(17)}}{{\mathit N}}$ , ${{\mathit X}{(17)}}$ $\rightarrow$ ${{\mathit e}^{+}}{{\mathit e}^{-}}$
26
LEES
2015E
 BABR ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions
27
ADAMS
1997B
 KTEV $\mathit m$= $1.2 - 5$ GeV
$<10^{-36} - 10^{-33}$ 90 28
GALLAS
1995
TOF $\mathit m$= $0.5 - 20$ GeV
$<(4 - 0.3){\times }\text{ 10}$$^{-31}$ 95 29
AKESSON
1991
CNTR $\mathit m$ = $0 - 5$ GeV
$<2 \times 10^{-36}$ 90 30
BADIER
1986
BDMP $\tau $ = (0.05$-1.){\times }10^{-8}$s
$<2.5 \times 10^{-35}$ 31
GUSTAFSON
1976
CNTR $\tau $ $>10^{-7}$ s
1  TUMASYAN 2022AG search for strongly interacting neutral massive particles via trackless jets with 16.1 fb${}^{-1}$ at 13 TeV; no signal detected; limits placed in mass vs. cross section plane for various simplified models.
2  AAD 2021F search for hard monojet production at ATLAS with 139 ${}^{-1}$ of 13 TeV data. No signal observed. Limits placed on invisible production cross-section recoiling against ISR and interpreted in variety of BSM models.
3  AAIJ 2020AL search for dimuon resonance from promptly decaying ${{\mathit X}}$ particle; no signal; limits placed on m(${{\mathit X}}$) up to 60 GeV depending on mixing in 2HDM .
4  SIRUNYAN 2020AY measured ${{\mathit \Upsilon}}$(1S) pair production cross section and searched for new states decaying into ${{\mathit \Upsilon}{(1S)}}{{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ at CMS with 13 TeV with 35.9 fb${}^{-1}$. No signal is found and limits are set in ${{\mathit \sigma}}\cdot{}$BF vs. mass plane for tetra-${{\mathit b}}$-quarks with masses between 17.5 and 19 GeV and for generic search for narrow resonances with mass between 16.5 and 27 GeV.
5  SIRUNYAN 2020Z search for BSM physics via multilepton production with CMS at 13 TeV with 137 fb${}^{-1}$; no signal is found and limits are set on type-III seesaw and other BSM models.
6  AABOUD 2019H searches for di-photon-jet resonance at 13 TeV and 36.7 fb${}^{-1}$ of data; no signal found and limits placed on ${{\mathit \sigma}}\cdot{}$BR vs. mass plane for various simplified models.
7  AABOUD 2019V review ATLAS searches for mediator-based DM at 7, 8, and 13 TeV with up to 37 fb${}^{-1}$ of data; no signal found and limits set for wide variety of simplified models of dark matter.
8  SIRUNYAN 2019O search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \gamma}}$ $\not E_T$ at 13 TeV with 36.1 fb${}^{-1}$; no signal found and limits set for various simplified models.
9  AABOUD 2018CJ make multichannel search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit V}}{{\mathit V}}$ $/$ ${{\mathit \ell}}{{\mathit \ell}}$ $/$ ${{\mathit \ell}}{{\mathit \nu}}$ , ${{\mathit V}}$ = ${{\mathit W}},{{\mathit Z}},{{\mathit h}}$ at 13 TeV, 36.1 fb${}^{-1}$; no signal found; limits placed for several BSM models.
10  AABOUD 2018CM search for lepton-flavor violating resonance in ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit e}}{{\mathit \mu}}$ $/$ ${{\mathit e}}{{\mathit \tau}}$ $/$ ${{\mathit \mu}}{{\mathit \tau}}$ at 13 TeV, 36.1 fb${}^{-1}$; no signal is found and limits placed for various BSM models.
11  AAIJ 2018AJ search for prompt and delayed dark photon decay ${{\mathit A}^{\,'}}$ $\rightarrow$ ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ at LHCb detector using 1.6 fb${}^{-1}$ of ${{\mathit p}}{{\mathit p}}$ collisions at 13 TeV; limits on m(${{\mathit A}^{\,'}}$) vs. kinetic mixing are set.
12  BANERJEE 2018 search for dark photon ${{\mathit A}^{\,'}}$/16.7 MeV boson ${{\mathit X}}$ at NA64 via ${{\mathit e}}$ ${{\mathit Z}}$ $\rightarrow$ ${{\mathit e}}{{\mathit Z}}{{\mathit X}}$( ${{\mathit A}^{\,'}}$); no signal found and limits set on the ${{\mathit X}}-{{\mathit e}^{-}}$ coupling ${{\mathit \epsilon}_{{{e}}}}$ in the range $1.3 \times 10^{-4}{}\leq{}{{\mathit \epsilon}_{{{e}}}}{}\leq{}4.2 \times 10^{-4}$ excluding part of the allowed parameter space.
13  BANERJEE 2018A search for invisibly decaying dark photons in ${{\mathit e}}$ ${{\mathit Z}}$ $\rightarrow$ ${{\mathit e}}{{\mathit Z}}{{\mathit A}^{\,'}}$ , ${{\mathit A}^{\,'}}$ $\rightarrow$ invisible; no signal found and limits set on mixing for m(${{\mathit A}^{\,'}}$) $<$ 1 GeV.
14  MARSICANO 2018 search for dark photon ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit A}^{\,'}}$( ${{\mathit \gamma}}$) visible decay in SLAC E137 ${{\mathit e}}$ beam dump data. No signal observed and limits set in ${{\mathit \epsilon}}$ coupling vs m(${{\mathit A}^{\,'}}$) plane, see their figure 7.
15  SIRUNYAN 2018BB search for high mass dilepton resonance; no signal found and exclude portions of p-space of ${{\mathit Z}^{\,'}}$, KK graviton models.
16  SIRUNYAN 2018DA search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ Black Hole, string ball, sphaleron via high multiplicity events at 13 TeV, 35.9 fb${}^{-1}$; no signal, require e.g. m(BH) $>$ 10.1 TeV.
17  SIRUNYAN 2018DD search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit j}}{{\mathit j}}$ deviations in dijet angular distribution. No signal observed. Set limits on large extra dimensions, black holes and DM mediators e.g. m(BH) $>$ $5.9 - 8.2$ TeV.
18  SIRUNYAN 2018DR search for dimuon resonance in ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit b}}{{\mathit \mu}}{{\overline{\mathit \mu}}}$ at 8 and 13 TeV. Slight excess seen at m( ${{\mathit \mu}}{{\overline{\mathit \mu}}}$ ) $\sim{}$ 28 GeV in some channels.
19  SIRUNYAN 2018DU search for high mass diphoton resonance in ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit \gamma}}{{\mathit \gamma}}$ at 13 TeV using 35.9 fb${}^{-1}$; no signal; limits placed on RS Graviton, LED, and clockwork.
20  SIRUNYAN 2018ED search for ${{\mathit p}}$ ${{\mathit p}}$ $\rightarrow$ ${{\mathit V}}$ $\rightarrow$ ${{\mathit W}}{{\mathit h}}$ ; ${{\mathit h}}$ $\rightarrow$ ${{\mathit b}}{{\overline{\mathit b}}}$ ; ${{\mathit W}}$ $\rightarrow$ ${{\mathit \ell}}{{\mathit \nu}}$ at 13 TeV with 35.9 fb${}^{-1}$; no signal; limits set on m(${{\mathit W}^{\,'}}$) $>$ 2.9 TeV.
21  AABOUD 2017B exclude m(${{\mathit W}^{\,'}}$, ${{\mathit Z}^{\,'}}$) $<1.49 - 2.31$ TeV depending on the couplings and ${{\mathit W}^{\,'}}/{{\mathit Z}^{\,'}}$ degeneracy assumptions via ${{\mathit W}}{{\mathit H}}$ , ${{\mathit Z}}{{\mathit H}}$ search in ${{\mathit p}}{{\mathit p}}$ collisions at 13 TeV with 3.2$~$fb${}^{-1}$ of data.
22  AAIJ 2017BR search for long-lived hidden valley pions from Higgs decay. Limits are set on the signal strength as a function of the mass and lifetime of the long-lived particle in their Fig. 4 and Tab. 4.
23  AAD 2016O search for high $\mathit E_{T}{{\mathit \ell}}$ + (${{\mathit \ell}}$s or jets) with 3.2 fb${}^{-1}$ at 13 TeV; exclude micro black holes mass $<$ 8 TeV (Fig. 3) for models with two extra dimensions.
24  AAD 2016R search for ${{\mathit W}}{{\mathit W}}$ , ${{\mathit W}}{{\mathit Z}}$ , resonance in 20.3 fb${}^{-1}$ at 8 TeV data; limits placed on massive RS graviton (Fig. 4).
25  KRASZNAHORKAY 2016 report ${{\mathit p}}$ ${}^{7}{}^{}\mathrm {Li}$ $\rightarrow$ ${}^{8}{}^{}\mathrm {Be}$ $\rightarrow$ ${{\mathit e}}$ ${{\overline{\mathit e}}}$ ${{\mathit N}}$ 5${{\mathit \sigma}}$ resonance at 16.7 MeV-- possible evidence for nuclear interference or new light boson . However, such nuclear interference was ruled out already by ZANG 2017 .
26  LEES 2015E search for long-lived neutral particles produced in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ collisions in the Upsilon region, which decays into ${{\mathit e}^{+}}{{\mathit e}^{-}}$ , ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ , ${{\mathit e}^{\pm}}{{\mathit \mu}^{\mp}}$ , ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ , ${{\mathit K}^{+}}{{\mathit K}^{-}}$ , or ${{\mathit \pi}^{\pm}}{{\mathit K}^{\mp}}$ . See their Fig. 2 for cross section limits.
27  ADAMS 1997B search for a hadron-like neutral particle produced in ${{\mathit p}}{{\mathit N}}$ interactions, which decays into a ${{\mathit \rho}^{0}}$ and a weakly interacting massive particle. Upper limits are given for the ratio to ${{\mathit K}_{{{L}}}}~$production for the mass range $1.2 - 5$ GeV and lifetime $10^{-9} - 10^{-4}~$s. See also our Light Gluino Section.
28  GALLAS 1995 limit is for a weakly interacting neutral particle produced in 800 GeV/$\mathit c$ ${{\mathit p}}{{\mathit N}}$ interactions decaying with a lifetime of $10^{-4} - 10^{-8}~$s. See their Figs.$~$8 and 9. Similar limits are obtained for a stable particle with interaction cross section $10^{-29} - 10^{-33}$ cm${}^{2}$. See Fig.$~$10.
29  AKESSON 1991 limit is from weakly interacting neutral long-lived particles produced in ${{\mathit p}}{{\mathit N}}$ reaction at 450 GeV/$\mathit c$ performed at CERN$~$SPS. Bourquin-Gaillard formula is used as the production model. The above limit is for $\tau ~>~10^{-7}~$s. For $\tau ~>~10^{-9}~$s, $\sigma ~<~10^{-30}~$cm${}^{−2}$/nucleon is obtained.
30  BADIER 1986 looked for long-lived particles at 300 GeV ${{\mathit \pi}^{-}}$ beam dump. The limit applies for nonstrongly interacting neutral or charged particles with mass $>$2 GeV. The limit applies for particle modes, ${{\mathit \mu}^{+}}{{\mathit \pi}^{-}}$ , ${{\mathit \mu}^{+}}{{\mathit \mu}^{-}}$ , ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ X, ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}{{\mathit \pi}^{\pm}}$ etc. See their figure 5 for the contours of limits in the mass-$\tau $ plane for each mode.
31  GUSTAFSON 1976 is a 300 GeV FNAL experiment looking for heavy ($\mathit m$ $>$2 GeV) long-lived neutral hadrons in the M4 neutral beam. The above typical value is for $\mathit m$ = 3 GeV and assumes an interaction cross section of 1 mb. Values as a function of mass and interaction cross section are given in figure 2.
References:
TUMASYAN 2022AG
EPJ C82 213 Search for strongly interacting massive particles generating trackless jets in proton?proton collisions at $\sqrt{s} = 13\,\text {TeV} $
AAD 2021F
PR D103 112006 Search for new phenomena in events with an energetic jet and missing transverse momentum in $pp$ collisions at $\sqrt {s}$ =13 TeV with the ATLAS detector
AAIJ 2020AL
JHEP 2010 156 Searches for low-mass dimuon resonances
SIRUNYAN 2020AY
PL B808 135578 Measurement of the $\Upsilon$(1S) pair production cross section and search for resonances decaying to $\Upsilon$(1S)$\mu^+\mu^-$ in proton-proton collisions at $\sqrt{s} =$ 13 TeV
SIRUNYAN 2020Z
JHEP 2003 051 Search for physics beyond the standard model in multilepton final states in proton-proton collisions at $\sqrt{s} =$ 13 TeV
AABOUD 2019V
JHEP 1905 142 Constraints on mediator-based dark matter and scalar dark energy models using $\sqrt s = 13$ TeV $pp$ collision data collected by the ATLAS detector
AABOUD 2019H
PR D99 012008 A search for pairs of highly collimated photon-jets in $pp$ collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector
SIRUNYAN 2019O
JHEP 1902 074 Search for new physics in final states with a single photon and missing transverse momentum in proton-proton collisions at $\sqrt{s} =$ 13 TeV
AABOUD 2018CJ
PR D98 052008 Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36??fb$^{-1}$ of proton-proton collision data at $\sqrt{s} = 13$ TeV with the ATLAS detector
AABOUD 2018CM
PR D98 092008 Search for lepton-flavor violation in different-flavor, high-mass final states in $pp$ collisions at $\sqrt s=13$ TeV with the ATLAS detector
AAIJ 2018AJ
PRL 120 061801 Search for Dark Photons Produced in 13 TeV $pp$ Collisions
BANERJEE 2018
PRL 120 231802 Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN
BANERJEE 2018A
PR D97 072002 Search for vector mediator of Dark Matter production in invisible decay mode
MARSICANO 2018
PR D98 015031 Dark photon production through positron annihilation in beam-dump experiments
SIRUNYAN 2018DD
EPJ C78 789 Search for new physics in dijet angular distributions using proton?proton collisions at $\sqrt{s}=$ 13 TeV and constraints on dark matter and other models
SIRUNYAN 2018ED
JHEP 1811 172 Search for heavy resonances decaying into a vector boson and a Higgs boson in final states with charged leptons, neutrinos and b quarks at $ \sqrt{s}=13 $ TeV
SIRUNYAN 2018BB
JHEP 1806 120 Search for high-mass resonances in dilepton final states in proton-proton collisions at $\sqrt{s}=$ 13 TeV
SIRUNYAN 2018DU
PR D98 092001 Search for physics beyond the standard model in high-mass diphoton events from proton-proton collisions at $\sqrt{s} =$ 13 TeV
SIRUNYAN 2018DA
JHEP 1811 042 Search for black holes and sphalerons in high-multiplicity final states in proton-proton collisions at $ \sqrt{s}=13 $ TeV
SIRUNYAN 2018DR
JHEP 1811 161 Search for resonances in the mass spectrum of muon pairs produced in association with b quark jets in proton-proton collisions at $\sqrt{s} =$ 8 and 13 TeV
AABOUD 2017B
PL B765 32 Search for New Resonances Decaying to a ${{\mathit W}}$ or ${{\mathit Z}}$ Boson and a Higgs Boson in the ${{\mathit \ell}^{+}}{{\mathit \ell}^{-}}{\mathit {\mathit b}}{\mathit {\overline{\mathit b}}}$, ${{\mathit \ell}}{{\mathit \nu}}{\mathit {\mathit b}}{\mathit {\overline{\mathit b}}}$, and ${{\mathit \nu}}{{\overline{\mathit \nu}}}{\mathit {\mathit b}}{\mathit {\overline{\mathit b}}}$ Channels with ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 13 TeV with the ATLAS Detector
AAIJ 2017BR
EPJ C77 812 Updated Search for Long-Lived Particles Decaying to Jet Pairs
AAD 2016R
PL B755 285 Combination of Searches for ${{\mathit W}}{{\mathit W}}$, ${{\mathit W}}{{\mathit Z}}$, and ${{\mathit Z}}{{\mathit Z}}$ Resonances in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 8 TeV with the ATLAS Detector
AAD 2016O
PL B760 520 Search for TeV-Scale Gravity Signatures in High-Mass Final States with Leptons and Jets with the ATLAS Detector at $\sqrt {s }$ = 13 TeV
KRASZNAHORKAY 2016
PRL 116 042501 Observation of Anomalous Internal Pair Creation in Be8 : A Possible Indication of a Light, Neutral Boson
LEES 2015E
PRL 114 171801 Search for Long-Lived Particles in ${{\mathit e}^{+}}{{\mathit e}^{-}}$ Collisions
ADAMS 1997B
PRL 79 4083 Search for Light Gluinos via the Spontaneous Appearance of ${{\mathit \pi}^{+}}{{\mathit \pi}^{-}}$ Pairs with an 800 ${\mathrm {GeV/}}\mathit c$ Proton Beam at Fermilab
GALLAS 1995
PR D52 6 Search for Neutral Weakly Interacting Massive Particles in the Fermilab Tevatron Wide Band Neutrino Beam
AKESSON 1991
ZPHY C52 219 A Search for Weakly Interacting Neutral Particles in Missing Energy Events on 450 ${\mathrm {GeV/}}\mathit c$ ${{\mathit p}}{{\mathit N}}$ Collisions
BADIER 1986
ZPHY C31 21 Mass and Lifetime Limits on New Longlived Particles in 300 ${\mathrm {GeV/}}\mathit c$ ${{\mathit \pi}^{-}}$ Interactions
GUSTAFSON 1976
PRL 37 474 Search for New Massive Longlived Neutral Particles