Table Of ContentEUROPEAN ORGANISATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP-2014-228
Submitted to: Physics Letters B
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1
0
2 Search for pair-produced long-lived neutral particles decaying
r
a to jets in the ATLAS hadronic calorimeter in pp collisions at
√
M
s = 8 TeV
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The ATLAS Collaboration
e
h
[
2
v
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2 Abstract
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0 The ATLAS detector at the Large Hadron Collider at CERN is used to search for the decay of
.
1 a scalar boson to a pair of long-lived particles, neutral under the Standard Model gauge group, in
√
0 20.3 fb−1 of data collected in proton–proton collisions at s=8 TeV. This search is sensitive to long-
5
1 lived particles that decay to Standard Model particles producing jets at the outer edge of the ATLAS
:
v electromagnetic calorimeter or inside the hadronic calorimeter. No significant excess of events is
i observed. Limits are reported on the product of the scalar boson production cross section times
X
branching ratio into long-lived neutral particles as a function of the proper lifetime of the particles.
r
a
Limits are reported for boson masses from 100 GeV to 900 GeV, and a long-lived neutral particle
mass from 10 GeV to 150 GeV.
(cid:13)c 2015CERNforthebenefitoftheATLASCollaboration.
ReproductionofthisarticleorpartsofitisallowedasspecifiedintheCC-BY-3.0license.
Search for pair-produced long-lived neutral particles decaying to jets in the ATLAS
√
hadronic calorimeter in pp collisions at s = 8 TeV
TheATLASCollaboration
Abstract
TheATLASdetectorattheLargeHadronCollideratCERNisusedtosearchforthedecayofascalarbosontoapairoflong-lived
√
particles,neutralundertheStandardModelgaugegroup,in20.3fb−1ofdatacollectedinproton–protoncollisionsat s=8TeV.
Thissearchissensitivetolong-livedparticlesthatdecaytoStandardModelparticlesproducingjetsattheouteredgeoftheATLAS
electromagneticcalorimeterorinsidethehadroniccalorimeter. Nosignificantexcessofeventsisobserved. Limitsarereportedon
theproductofthescalarbosonproductioncrosssectiontimesbranchingratiointolong-livedneutralparticlesasafunctionofthe
properlifetimeoftheparticles. Limitsarereportedforbosonmassesfrom100GeVto900GeV,andalong-livedneutralparticle
massfrom10GeVto150GeV.
Keywords: high-energycolliderexperiment,long-livedneutralparticle,newphysics
1. Introduction cay deep inside the calorimeter is reconstructed as a jet with
an unusual energy signature that most traditional searches re-
ThediscoveryoftheHiggs boson[1–3]bytheATLASand ject as having poor data quality. This search focusses on fi-
CMS experiments [4, 5] in 2012 identified the last piece of nal states where both π decay in the hadronic calorimeter or
v
the highly successful Standard Model (SM). Subsequent mea- near the outer edge of the electromagnetic calorimeter. Each
surements of the Higgs boson branching ratios and couplings, heavyfermionpairfromaπ decayisreconstructedasasingle
v
whileconsistentwiththeSMexpectations,allowforasubstan- calorimeterjetwiththreecharacteristicproperties:anarrowra-
tial branching ratio to exotic particles. This letter describes a dius, no tracks from charged particles matched to the jet, and
searchfordecaysoftheHiggsbosonandotherscalarbosonsto littleornoenergydepositedintheelectromagneticcalorimeter.
non-SMstatesthatinturndecaytoSMparticles. Scalar boson masses ranging from 100 GeV to 900 GeV
A number of extensions of the SM involve a hidden sector are considered in addition to the Higgs boson’s mass (gener-
that is weakly coupled to the SM, with the two connected via ated at m =126 GeV) and π masses between 10 GeV and
H v
acommunicatorparticle. Thisletterconsidersmodelscontain- 150GeVarestudied. Othersearchesforpairsofdisplacedver-
ing a hidden sector with a confining gauge interaction that is tices generated by pair-produced neutral, long-lived particles
otherwise invisible to the SM. The communicator is chosen wereperformedinATLAS[11]andCMS[12]attheLHCand
to be a SM-sector scalar boson, Φ [6–9]. The communicator inD0[13]andCDF[14]attheTevatron. TheTevatronexper-
mixes with a hidden-sector scalar boson, Φhs, which decays imentsandCMSsearchedfordisplacedverticesintheirtrack-
into detectable SM particles. This search considers commu- ingsystemonly,whichresultsinacorrespondingproperdecay
nicatormassesbetween100GeVand900GeV.AΦmassclose length range of a few meters. CMS also looked at the multi-
tothemassofthediscoveredHiggsbosonisincludedtosearch lepton decay channel, another possible decay of HV particles.
forexoticdecaysoftheHiggsboson. The previous ATLAS analysis, based on 7 TeV data, used the
AHiddenValley(HV)model[8,9]isusedasthebenchmark muonspectrometerandissensitivetoproperdecaylengthsbe-
model.ThelightestHVparticlesformanisospintripletofpseu- tween0.5mand27m,dependingonthebenchmarkmodel.No
doscalar particles which are called valley pions (πv) because evidenceofphysicsbeyondtheSMwasfound.
of their similarity to the SM triplet. The π are pair-produced
v
(Φ →π π ) and each decays to a pair of SM fermions. The
hs v v
π possess Yukawa couplings to fermions and therefore pref-
v 2. TheATLASdetector
erentiallydecaytoaccessibleheavyfermions,primarilybb,cc
andτ+τ−.
The lifetime of the π is unconstrained and could be quite The ATLAS detector [15] is a multi-purpose detector at the
v
long. A long-lived π can result in signatures that traditional LHC,consistingofseveralsub-detectors. Fromtheinteraction
v
searches fail to detect. If a π decays in the inner detector or point (IP) outwards there are an inner detector (ID), electro-
v
muonspectrometer, itcanbereconstructedasadisplacedver- magneticandhadroniccalorimeters, andamuonspectrometer
tex. However, standard vertex-finding algorithms [10] are not (MS).TheID,immersedina2Taxialmagneticfield,provides
likelytoreconstructitwithoutmodification. Likewise,aπ de- trackingandvertexinformationforchargedparticleswithinthe
v
PreprintsubmittedtoElsevier March10,2015
pseudorapidity1 (η)region|η|<2.5. Itconsistsofthreedif- of the detector response with GEANT4 [19, 20] and the same
ferenttrackingdetectors. Fromsmallradiioutwards,theseare reconstruction algorithms as are used on the data. GEANT4
asiliconpixeldetector,asiliconmicrostriptracker(SCT)anda needednomodificationtosimulatethesignalasalldecayparti-
transitionradiationtracker(TRT). clesareSMparticles. AllMCsamplesarereweightedtorepro-
Thecalorimeterprovidescoverageovertherange|η|<4.9. ducethenumberofinteractionsperbunchcrossingobservedin
It consists of a lead/liquid-argon electromagnetic calorimeter thedata.
(ECal) at smaller radii surrounded by a hadronic calorimeter
Table1: TheΦmassorHiggsbosonmass,Φgluonfusionproductioncross
(HCal) at larger radii comprising a steel and scintillator-tile
section,andπvmassofeachbenchmarkHiddenValleymodelgenerated. The
systeminthebarrelregion(|η|<1.7)andaliquid-argonsys- cross-sectionsarebasedontheassumptioninthebenchmarkedmodelthatthe
tem with copper absorbers in the endcaps (1.5<|η|<3.2). Φ boson production mechanism is the same as the Higgs boson production
The ECal spans the range 1.5m < r < 2.0 m in the barrel mechanism.Thedecaybranchingratiosoftheπv asafunctionoftheπvmass
arelistedinthesecondtableasdeterminedinthesimulationsamples.
and 3.6m<|z|<4.25 m in the endcaps. The HCal covers
2.25m<r <4.25 m in the barrel and 4.3m<|z|<6.05 m
in the endcaps. There is also a forward calorimeter (FCal), mH σ πvMass
withcoveragebetween3.1<|η|<4.9,whichusescopperab- [GeV] [pb] [GeV]
sorbers in the first layer, and tungsten absorbers in the second 126 19.0 10,25,40
and third layers, and liquid-argon as the active medium in all
layers. Muon identification and momentum measurement are ΦMass σ π Mass
v
provided by the MS, which extends to |η|= 2.7. It consists [GeV] [pb] [GeV]
of a three-layer system of gas-filled precision-tracking cham-
100 29.7 10,25
bers. The region |η|< 2.4 is also covered by separate trigger
140 15.4 10,20,40
chambers.
300 3.59 50
A sequential three-level trigger system selects events to be
600 0.52 50,150
recordedforofflineanalysis. Thefirstlevelconsistsofcustom
900 0.06 50,150
hardwarethatimplementsselectiononjets,electrons,photons,
τ leptons, muons, and missing transverse momentum or large
π Mass BRbb BRτ+τ− BRcc
totaltransverseenergy.Thesecondandthirdlevelsaddcharged v
[GeV] [%] [%] [%]
particle track finding and refine the first-level selections with
progressivelymoredetailedalgorithms. 10 70.0 16.4 13.4
20 86.3 8.0 5.6
25 86.6 8.1 5.3
3. Dataandsimulationsamples
40 86.5 8.5 5.0
50 86.2 8.8 4.9
Alldatausedinthisanalysiswerecollectedduringthe2012
150 84.8 10.2 4.8
LHC proton-proton run at a centre-of-mass energy of 8 TeV.
After data quality requirements are applied, the sample corre-
spondstoanintegratedluminosityof20.3fb−1.TheHVMonte
Carlo (MC) samples are generated with PYTHIA 8.165 [16]
andthePDFMSTW2008[17]tosimulategluonfusiongg→Φ 4. Triggerandeventselection
production and the Φ decay Φ →π π for different Φ and
hs hs v v
Candidate events are collected using a dedicated trigger,
π masses (Table 1). Φ masses below 300 GeV are consid-
v
called the CalRatio trigger [21], which looks specifically for
ered low-mass samples and the rest are considered high-mass
long-lived neutral particles that decay near the outer radius of
samples. Theπ lifetimeisfixedineachsampletoensurede-
v
the ECal or within the HCal. The trigger is tuned to look for
cays throughout the ATLAS detector. The Φ is simulated in
events containing at least one narrow jet with little energy de-
PYTHIAbyreplacingtheHiggsbosonwiththeΦandhaving
posited in the ECal and no charged tracks pointing towards
the Φ decay to π 100% of the time. The Φ samples are pro-
v
the jet. At the first level the trigger selects only narrow jets
ducedwithcrosssectionscalculatedatnext-to-next-to-leading-
by requiring at least 40 GeV of transverse energy (E ) in the
logarithmicaccuracyinQCDprocessesandatnext-to-leading- T
calorimeter in a 0.2×0.2 (∆η×∆φ) region using topological
order in electro-weak processes assuming the Φ at each mass
jets [15, 22], in contrast to the default algorithm in which the
has the same properties as the SM Higgs boson [18]. After
energyina0.4×0.4regionissummed. The40GeVE thresh-
generationthe eventsare passedthrougha detailedsimulation T
oldrequirementisfullyefficientatanofflinejetE of60GeV.
T
To select jets with a high fraction of their energy in the HCal
1ATLASusesaright-handedcoordinatesystemwithitsoriginatthenom- thesecondlevelofthetriggerrequiresthesenarrowjetstohave
inalinteractionpoint(IP)inthecentreofthedetectorandthez-axisalongthe log (E /E )>1.2,whereE /E istheratiooftheenergy
10 H EM H EM
beampipe.Thex-axispointsfromtheIPtothecentreoftheLHCring,andthe depositedintheHCal(E )totheenergydepositedintheECal
y-axispointsupward. Cylindricalcoordinates(r,φ)areusedinthetransverse H
(E ). Thetriggeralsorequiresnotrackswith p >1GeVin
plane,φ beingtheazimuthalanglearoundthebeampipe. Thepseudorapidity EM T
isdefinedintermsofthepolarangleθasη=−lntan(θ/2). the region 0.2×0.2 (∆η×∆φ) around the jet axis. The third
2
levelofthetriggerusestheslowerbutmoreaccurateanti-k al- Events also contain a reconstructed primary vertex with at
t
gorithm[23]withR=0.4toreconstructthejetandrequiresthe least three tracks with p >1 GeV. Events are rejected if any
T
jettohaveaminimumof35GeVoftransverseenergy. reconstructed jets show evidence of being caused by a beam-
halointeraction[21]. Amissingtransversemomentumrequire-
Theprobability(ε )forasingleπ tofirethetriggerinsim-
πv v ment,Emiss<50GeV,isappliedtorejectnon-collisionevents,
ulatedeventsisshowninFig.1,forthe(a)barreland(b)end- T
suchascosmicraysorbeam-halointeractions.
capregionofthecalorimeterinseveraldifferentsignalsamples.
Intheofflineselection,jetsarereconstructedwithananti-k
Theaverageprobabilityforthelow(high)scalarbosonmasses t
algorithmwithR=0.4,startingfromcalorimeterenergyclus-
is about 20% (55%) for π decays occurring at radii between
v
ters calibrated using the local cluster weighting method [24].
2.0mand3.5minthebarrel, andabout6%(30%)forπ de-
v
Jets are then calibrated using an energy- and η-dependent
cays with |z| between 4.0 m and 5.5 m in the endcaps. The
simulation-based calibration scheme. Jets are rejected if they
turn-on takes place before the inner edge of the HCAL as the
do not satisfy the standard ATLAS good-jet criteria with the
log (E /E )cutallowsforasmallamountofenergyinthe
10 H EM
exception of requirements that reject jets with small electro-
ECal. Theprobabilitydecreasestowardstheouterregionofthe
magnetic energy fraction (EMF) [25]. At least one jet must
HCal where too much of the energy escapes the HCal to pass
have fired the CalRatio trigger. The jet matching the trigger
the jet E requirement. The efficiency is lower in the endcaps
T
mustpassanE >60GeVrequirementwhileasecondjetmust
because events tend to not satisfy the isolation criteria due to T
satisfyanE >40GeVrequirement. Ifmorethanonejetfired
theincreasedoccupancyfromextracollisioneventsinthesame T
theCalRatiotriggerthenonlytheleadingjetisrequiredtohave
bunchcrossingasahard-scatterinteraction(pile-up).
E >60GeV.
T
Individually, all jets must satisfy |η| < 2.5, have
log (E /E )>1.2,andhavenogoodtracksintheIDwith
py v 0.6 mH 126 GeV - mpv 10 GeV pT1>01 GHeVEiMn a region ∆R<0.22 centred on the jet axis. A
babilit 0.5 mmHH 112460 GGeeVV -- mmppvv 2450 GGeeVV ganododattroatcaklomfuatstlehaasvteniantelheiatsstintwtohehpitisxeilnanthdeSpCixTeldedteetcetcotrosr.
o
pr Fig.2(a)comparesthedistributionofthenumberofgoodtracks
0.4 mF 300 GeV - mpv 50 GeV associatedwitheachjetinthemulti-jetsample(describedinthe
mF 600 GeV - mpv 150 GeV
0.3 mF 900 GeV - mpv 150 GeV next section) with that in jets resulting from simulated πv de-
caysintheHCALorID.Fig.2(b)makesthesamecomparison
ATLAS
0.2 Simulation forthedistributionoflog10(EH/EEM)ofeachjet. Themulti-jet
datawasgatheredusingaprescaled,single-jettriggerwitha15
barrel
0.1 GeVrequirement.
Jets caused by cosmic rays and beam-halo interactions are
0 often out-of-time. The jet timing is calculated by making an
1 1.5 2 2.5 3 3.5 4 4.5 5
energy-weighted average of the timing for each cell in the jet.
r[m]
Each cell is defined to have a time of 0 ns if its energy is
recorded at a time consistent with the arrival of a β =1 par-
(a)
ticle from the IP. The timing of each jet is required to satisfy
−1<t <5 ns. This cut will impact the efficiency for low β
v
pobability 00..56 ASTimLuAlaStion mmmmHHHF 111322406600 GGGGeeeeVVVV ---- mmmmppppvvvv 12450500 GGGGeeeeVVVV πβthv-e.dihDsitugriehbtumotiatohsnseiΦrseqpsueaiamrkepemldeesnnetthaoerf1daihfffoiegrrhel-onEwcTemjbeeattsiwsneΦtehnissamamnΦpallayenssd.ismFthoπevr
pr endcap mF 600 GeV - mpv 150 GeV resultsinalargeboostfortheπv atthegeneratedlifetimes. As
0.4 mF 900 GeV - mpv 150 GeV aresult,theinefficiencyintroducedbythetimingcutisatworst
1.5%fortheconsideredsamples.
0.3
The analysis requires that exactly two jets satisfy these re-
quirements. The second jet requirement significantly reduces
0.2
theSMmulti-jetbackgroundcontribution. Table3liststhefi-
nalnumberofexpectedeventsineachsignalMCsample. The
0.1
finalnumberofeventsselectedindatais24.
0
3.5 4 4.5 5 5.5 6
5. Backgroundestimation
z[m]
(b) The largest contribution to the expected background comes
from SM multi-jet events. Cosmic-ray interactions contribute
Fig.1:Theprobability(επv)forasingleπvtopassthetriggerasafunctionof
theπv(a)radialdecaylengthinthebarreland(b)thezpositionofthedecay
vertexintheendcapsforseveralΦandπvmasses. 2∆R= (cid:112)(∆η)2+(∆φ)2
3
Jets 10 (cid:242) L = 15 nb-1, s = 8 TeV ATLAS iEsTfy>th4e0mGoedVifiaenddA−TL2.A5S<goηo<d-j2e.t5c.riOtenrieajuesteidsbreyqtuhiereadnatolyssaist-.
of Multi-jets Thesecondisusedtomeasuretwoprobabilities: one,calledP,
n 1
Fractio SSiiggnnaall:: ddeeccaayy iinn HIDCal fmoernatjaentdtothpeasosthtehre, tcraigllgeedrQan,dfotrheaEjeTt>to6s0atGisfeyVtjheet rreeqquuiirree--
10-1
ment E >40 GeV. For both P and Q the jet must also pass
T
the log (E /E ), track isolation, and all other analysis jet
10 H EM
10-2 selectionrequirementsincludingthemodifiedATLASgood-jet
criteria. The probabilities are determined as a function of jet
10-3 ET andη. ThejetET andη dependenceiscalculatedindepen-
dentlybecausethesampleisnotlarge.Asystematicuncertainty
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 toaccountforanypotentialcorrelationisincludedintheanal-
n ysis. Tocalculatethissystematicuncertaintythechangeinthe
tracks
mean E as a function of η and the change in the mean η as
T
(a)
afunctionofE ismeasuredinthemulti-jetdatasample. The
T
maximum variation is 2% for both E and η. The E or η of
0.16 T T
of Jets 0.14 (cid:242) L = 15 nb-1, s = 8 TeV MuAltTi-LjeAtsS eaarechrejceatlacruelastyedst.emTahteicanlelwy sPhifatnedd Qbydtihsitsriabmutoiounnst aasrePuasenddtQo
n
o 0.12 Signal: decay in HCal estimate the multi-jet background as described below, and the
acti Signal: decay in ID maximumvariationintheresult(6%)isusedasthesystematic
Fr 0.1
uncertainty.
0.08 BinnedfitsoftheprobabilitiesasafunctionofE aremade
T
0.06 toaLandaufunctionandanexponentialfunctionforPandQ,
respectively. TheE requirementisignoredwhenfittingtoal-
0.04 T
low the curve to best match the distribution’s shape. The fit
0.02
errorsarepropagatedthroughtothesystematicinthemulti-jet
0 background. Theη dependenceisstronglycorrelatedwiththe
-3 -2 -1 0 1 2 3 4 5
distribution of material in the calorimeters and cannot be well
log (E /E )
10 H EM describedbyanysimplefunctionalform. Thustheprobability
(b) isobtaineddirectlyfromthedistribution.TheP(E )parameter-
T
isation is additionally split into leading jet and sub-leading jet
Fig.2:Distributionof(a)thenumberofgoodtracks(ntracks)withpT>1GeV samplesbecausetheprobabilityisdifferentforthetwotypesof
and∆R<0.2aroundthejetaxisand(b)thedistributionofjetlog10(EH/EEM) jets. ThiseffectisalsopresentforQ;however,itisaccounted
withjet|η|<2.5,pT>40GeV.Thedashedhistogramisforπvjetsdecaying
inthehadroniccalorimeter,andthedottedhistogramisforπvjetsdecayingin forbythecorrectionforjetcorrelationsdiscussedbelow. Plots
theID.BotharefromthemH =126GeV,mπv =10GeVsample. Thefilled of P(ET) and Q(ET) are shown in Fig. 3. The peak present
histogramisthemulti-jetdatasampleusedtoevaluatethemulti-jetcontribution
in P(E ) is the result of the trigger turn-on for the full trigger
tothebackground.EventsarerequiredtosatisfyEmiss<50GeV. T
T chain. The trigger jets are dominated by leading jets, and so
dominatedbytheleadingjetP.
The probability P is verified using the CalRatio-triggered
atamuchlowerlevel,andbeam-halointeractionsmakeaneg-
data. The CalRatio-triggered events are required to pass the
ligiblecontribution.
same event selection used to derive the single-jet probabilities
To estimate the multi-jet background contribution, a multi- as well as the requirements for calculating P. The CalRatio-
jetdatasampleisusedtoderivetheprobabilitythatajetpasses triggereddatacontains501387eventsthatfiredtheunprescaled
thetriggerandanalysisselection. Toobtainarawbackground CalRatio trigger and passed the required selection, and the
prediction, these jet probabilities are applied to a data sample single-jet probabilities predict 513000±94000 (statistical er-
that represents the multi-jet background before application of roronly)events.
jet-levelanalysisselection. Acorrectiontoaccountfortwo-jet To calculate the raw multi-jet background prediction the
correlations is applied to this raw prediction to yield the final probabilities P and Q are applied to jets in events selected by
multi-jetbackgroundestimate. the15GeVsingle-jettrigger. Thesesingle-jetprobabilitiesare
The multi-jet data sample contains events that pass single- combined into an event probability using a combinatoric cal-
jet triggers with an E threshold of 15 GeV or higher. These culation that requires at least one jet in the event to fire the
T
triggers were prescaled in 2012 and their effective luminosi- trigger and exactly two jets to pass all the jet selection crite-
ties range between 14.8 nb−1and 454.1 nb−1. The dataset is ria. The event probability is scaled to account for single-jet
representative of the full 20.3 fb−1 of data collected in 2012 triggerprescales,yieldingaweightforeachevent. Thesumof
and contains events from throughout the data collection pe- allweightsinthedatasampleyieldsarawbackgroundpredic-
riod. TheeventsarerequiredtopasstheanalysisEmissrequire- tion of 13.2 ± 2.9 (statistical ⊕ systematic error) events. The
T
ment and have at least two back-to-back (∆φ >2.0) jets with uncertaintyisdominatedbythesmallnumberofjetsfiringthe
4
log (E /E )andnumber-of-tracks(n )planethatareout-
· 10-6 10 H EM track
P (cid:242) side the signal region (log10(EH/EEM)>1.2 and ntrack =0).
16 L = 15 - 454 nb-1, s = 8 TeV Thelog10(EH/EEM)binningischosensuchthatbinningisuni-
14 Leading jets form in EMF,3. A range from 0 to 7 was used for ntrack. The
Sub-leading jets regionsoutsidethesignalregionareexpectedtohaveverylittle
12
ATLAS signalcontamination.
10
In each region the ratio of the number of events observed
8
in the CalRatio-triggered data to the raw prediction is calcu-
6 lated. Two series of ratios are calculated, one as a function of
4 log10(EH/EEM) and one as a function of ntrack. To determine
thetrendintheratioasafunctionoflog (E /E )then
2 10 H EM track
requirement is held constant: a jet is required to have 5 or 6
0
0 50 100 150 200 250 300 350 400 tracks.Theratioisthendeterminedforseveralnon-overlapping
E [GeV] rangesoflog (E /E ).Thesameprocedureisusedforn
T 10 H EM track
byrequiringjetstohave0.55<EMF<0.65. Becausetheratio
(a)
istakenwithrespecttotheobserveddata,thisratiowillcorrect
foranynormalisationerrorsinPorQ.
· 10-6 Both sets of ratios are fitted to allow extrapolation into the
Q (cid:242)
ATLAS L = 15 - 454 nb-1, s = 8 TeV signalregion. Theproductofthetworatiosinthesignalregion
25
yieldsascalefactortocorrectforthecorrelationbetweenjets.
Asystematicerrorisaddedtoaccountfortheassumptionthat
20
the two ratios are uncorrelated. The calculated scale factor is
1.8 ± 0.5. The uncertainty on the scale factor is due to the
15
limitedsamplesize.
10 To verify the procedure eight other bins on the
log (E /E ) and n plane were chosen and the full
10 H EM track
5 background prediction method was applied. Because signal
contamination is negligible outside of the signal region, the
0
0 50 100 150 200 250 300 350 400 predicted number of events can be directly compared to the
ET [GeV] number of events in the same log10(EH/EEM)–ntrack region
in the CalRatio-triggered data. In all cases the prediction is
(b)
consistentwithdatatowithinonestandarddeviation.
Thefinalmulti-jetpredictionis23.2±8.0(statistical⊕sys-
Fig. 3: The probability, P, that a jet from the multi-jet data sample passes
tematic error) events in the signal region. The uncertainty is
thetriggerandalljetrequirementsincludingtheET>60GeVrequirementis
shownin(a). ALandaufunctionisfittedtotheleadingandsub-leadingjet dominatedbythestatisticaluncertainty,whichisinturndomi-
distributionsseparately(solidanddashedlines).Theprobability,Q,topassall natedbythesmallnumberofjetsmatchingtheCalRatiotrigger
jetrequirementsincludingtheET>40GeVrequirementasafunctionofjetET inthemulti-jetdatasample.Thesystematiccontributioncomes
isshownin(b).Anexponentialfunctionisfittedtothedistribution(solidline).
fromthecorrelationbetweenE andη aswellasfromthein-
TheETrequirementisignoredwhenfittingtoallowthecurvetobestmatchthe T
shapeofthedata,butisusedexplicitlywhenPandQareappliedtoajet.The clusionofarequirementon∆φ (notusedinthesignalselection)
multi-jetdatawasgatheredusingarangeofprescaled,single-jettriggers. inthedeterminationofPandQ.
Particles from a cosmic-ray shower may pass through and
deposit energy in the calorimeter without passing through the
CalRatiotriggerinmulti-jetevents.
ID.Theseenergydepositscanbereconstructedastracklessjets.
In multi-jet events the log10(EH/EEM) and track isolation Theoverallcontributiontotheexpectedbackgroundisreduced
values of one jet are correlated with those of the second jet. bythejet-timingandEmissrequirements.
T
Ifaneventcontainsonejetofhighlog10(EH/EEM),thesecond Thecosmic-raybackgroundwasstudiedusingatriggersim-
jet is more likely to have high log10(EH/EEM) as well. Like- ilar to the CalRatio trigger, but active only during an empty
wise, if one jet has no tracks associated with it, the other is crossing. Eachprotonbeamisdividedupintobuckets,mostof
morelikelytohavenoassociatedtracksaswell. Thesingle-jet whicharefilledwithprotons. Anemptycrossingoccurswhen
probabilitiesaboveignorethiscorrelationbecauseeachiscal- an empty bucket in each beam coincides in the centre of the
culatedindependentlyofthelog10(EH/EEM)andntrackofother detector, and five buckets on either side in each beam are also
jets in the event. As a result, Q is lower than if it were cal- empty. Data gathered from these empty crossings are used to
culated only in events with an accompanying low ntrack, high studybackgroundsthatarenotbeamrelated.
log10(EH/EEM)jet. The analysis selection, with the exception of the jet-timing
A scale factor to account for the correlation is calculated requirementandthegood-vertexrequirement,areappliedtoall
fromthemulti-jetdatasampleandtheCalRatio-triggereddata
sample by examining numbers of events in regions in the 3log10(EH/EEM)=log10((1−EMF)/EMF).
5
eventstriggeredinemptycrossings. The−1<t<5nstiming 6. Systematicuncertainties
requirement is removed to retain more events to give a more
accuratedeterminationofthebackground.Asimplescalingcan Table 2 presents a summary of systematic uncertainties as-
beusedtopredicttheexpectedcosmic-rayeventratewithinthe sociatedwiththesignalsample. Theoveralluncertainty,taken
timing window because the arrival time of cosmic-ray muons as the sum in quadrature of all positive and negative contribu-
is uniformly distributed. It is found that about 5% of cosmic- tions respectively, is listed in the last column. The MC signal
ray events firing the trigger and containing two jets are events samples’ statistical uncertainty is shown in Table 3 and it is
wherebothjetssatisfythe−1<t<5nsrequirement. accountedforinthestatisticalanalysis. Theoverallnormalisa-
tion uncertainty of the integrated luminosity is 2.8% obtained
Two additional corrections are applied to determine the fi- following the same methodology as that detailed in Ref. [26]
nal background prediction due to cosmic-ray events. The first from a preliminary calibration of the luminosity scale derived
accounts for the different live-times of the triggers. The num- frombeam-separationscansperformedinNovember2012.The
ber of empty crossings is 2.9 times smaller than the number uncertainties on the Higgs boson production cross-sections at
√
used to collect the full data of 20.3 fb−1. The second correc- s=8TeV,whichareequaltotheuncertaintiesontheΦpro-
tionweightseacheventtoaccountforsofttracksduetopile-up ductioncross-sections,areabout10%[18].
and underlying-event effects that would have caused the jet to The uncertainty on the signal MC samples due to parton
failthetrackisolationrequirementhaditoccurredinacollision distributionfunctions(PDF)iscalculatedbyreweightingeach
environment. To determine the weights a trigger that selects eventusingthreedifferentPDFsets(MSTW2008nlo68cl[17],
randomcollisioneventsisusedtodeterminetheprobabilityas CT10[27],andNNPDF2.3[28])andtheirassociatederrorsets.
a function of η that a track with pT >1 GeV is present in a TheRMSchangeinacceptancefortheerrorsetsofeachPDF
∆R < 0.2 cone anywhere in the detector as a function of η. is calculated and combined with the difference in acceptances
This probability is applied to each jet in each event to deter- foreachofthethreePDFs.
mine an event weight. The event weights range from 0.55 to Pile-up primarily affects the acceptance by adding extra
0.63. Combiningallthecorrectionsresultsinapredictednum- tracksanddegradingthetrackisolationofajet. AllMCsam-
berofcosmic-rayeventsof0.3±0.2(statisticalerror). ples are reweighted to reproduce the observed distribution of
the number of interactions per bunch crossing in the data. To
Another possible background contribution comes from a
determine if pile-up is simulated properly in the MC samples,
beam-halo muon that undergoes bremsstrahlung in the HCal.
a direct comparison of data and MC multi-jet samples is per-
Two selection criteria reduce this type of background. A jet-
formed. The jet E , EMF, η, φ, associated tracks and timing
T
timing requirement is imposed because most of the jets pro-
distributions as a function of the mean number of pile-up in-
ducedbybeam-halointeractionsarenotcoincidentintimewith
teractions are compared in data and MC simulation. A 10%
jetsfrom ppinteractions. Inaddition,eventsarerejectedwhen
systematicuncertaintyisassignedtotheacceptancecoversall
tracksegmentsintheendcapmuonchambers,fromtheentering
theobserveddifferences.
beam-halomuon,aligninφ withajet. Thesetworequirements
Thejetenergyscale(JES)uncertaintyisevaluatedasafunc-
reducethebackgroundconsiderablywithnodiscernibleeffect
tionofthejetEMFandη,followingthesamestrategyusedin
onthesignal.
theinsitujetenergyintercalibration[24]. TheJESisrederived
forlowEMFjetsforthisanalysis. Therelativejetcalorimeter
Unpaired isolated crossings, i.e. crossings where only pro-
responseisstudiedbybalancingthetransversemomentaofdi-
tons from a single beam are present and at least three buckets
jets. The systematic uncertainty is obtained by comparing the
oneithersideoftheemptybeam’sbucketarealsoempty,canbe
p -balanceindatatothe p -balanceinMCsamples. Thisdif-
used to study beam-halo events. To estimate this background, T T
ferenceisusedtocalculateadifferenceintheJESindataand
artificial events are created by sampling two jets from a col-
MCsimulationandispropagatedtothesignalMCsamplesto
lection of jets passing both a CalRatio trigger active only dur-
getasystematicuncertaintyontheacceptance. Thisstudyalso
ingunpairedisolatedcrossingsandtheleadingjetrequirements
provides a useful performance comparison between data and
fromunpairedisolatedcrossings. Allpossiblepairsofjetsare
used and the Emiss <50 GeV requirement is applied to each MCjetsthatresemblesignaljets.
T The Emiss uncertainty accounts for variations in missing
constructed event. The number of jets passing the jet analysis T
transverse momentum scale and resolution [29]. The timing
selection and the fraction of constructed events satisfying the
Emiss requirement are combined to estimate the background. systematic accounts for mismodeling of jet timing between
T
MC and data. Both of these uncertainties were determined by
This method, which also accounts for cosmic-ray muon con-
smearingtheassociatedcuttodeterminetheimpactontheac-
tamination, predicts 0.07±0.07 events. The large uncertainty
ceptance.
isdueprimarilytothesmallnumberofjetspassingallrequired
cuts. The simulation of the trigger is verified by comparing the
performanceofthetriggerindatawiththeperformanceinMC
Backgroundsfromcombinationsofthesenon-beaminterac- simulation on the same multi-jet sample used to evaluate the
tions, i.e. a beam-halo jet plus a multi-jet, or a beam-halo jet multi-jetbackground. Eachtriggerrequirementisstudiedindi-
plusajetduetoacosmic-raymuon,werefoundtobenegligi- vidually:thejetE ,thelog (E /E ),andthetrackisolation.
T 10 H EM
ble. Eachrequirementisadjustedtomaketheperformancematchin
6
dataandMCevents,andtheresultingdifferencesinacceptance Table2:SummaryofsystematicuncertaintiesfortheΦandHiggsbosonpro-
ductioncross-section,jetenergyscale,trigger,missingtransversemomentum,
fromthenominalacceptance, foreachrequirement, areadded
andtherequirementonjettimingasapercentageofthesignalyield.Systematic
inquadraturetodeterminethesystematicuncertainty. errorsthathavecommonvaluesacrosssamplesarenotlisted(pile-upat10%,
The simulation of initial state radiation (ISR) cannot be di- ISRat+2.9%,andPDFat2.1%). Thelastcolumnreportsthetotalsystematic
−1.2
rectly verified because it is difficult to uniquely identify ISR uncertainty(includingtheluminosityandcommonsystematicerrors).
jets in data [30]. An incorrect ISR rate in the simulation im-
pactstheacceptancebyalteringthenumberofjetsintheevent Sample Hσ JES Trigger Emiss Time Total
andbyalteringtheboostoftheΦboson. Eachoftheseisstud- T
m ,m [%] [%] [%] [%] Cut [%]
ied independently. The ISR jet population is altered event by H πv
[GeV] [%]
eventsothatthenumberofISRjetsishalvedordoubled(jets
inMCsamplesarelabelledascontainingISRiftheycontaina 126,10 +10.4 +2.2 ±1.1 +5.5 +1.6 +16.4
−10.4 −2.7 −2.4 −6.6 −16.7
gluonwithp >2GeV).Thepopulationofπ jetsisnotaltered
T v 126,25 +10.4 +1.5 ±1.3 +3.1 +0.8 +15.6
bythisprocess, butanaddedISRjetmayoverlapwithoneof −10.4 −1.6 −1.8 −3.3 −15.5
theπ jets. TheeffectofaboostcausedbyanISRjetisstudied 126,40 +10.4 +2.6 ±1.1 +7.7 +1.9 +18.2
v −10.4 −6.2 −4.6 −5.9 −16.9
by exploiting the correlation between the π jet E and the Φ
v T
boost. FromRef.[30],theΦ p spectrumhasanuncertaintyof
T Sample Φσ JES Trigger Emiss Time Total
5%, which directly correlates with a 5% uncertainty in the π T
v
m ,m [%] [%] [%] [%] Cut [%]
jet energy. To calculate the systematic uncertainty associated Φ πv
[GeV] [%]
with the boost, the p of ISR jets is conservatively varied by
T
5%andthechangeinacceptanceisobserved. 100,10 +11.1 +2.3 ±0.1 +4.6 +2.7 +16.7
−10.6 −4.0 −3.4 −9.5 −18.5
ThechangesinacceptancefrombothsourcesofISRuncer-
100,25 +11.1 +5.5 ±1.2 +3.4 +1.7 +17.0
taintyaretakenascorrelatedsystematicerrorsandaddedtoget −10.6 −3.7 −2.5 −0.7 −15.8
thetotalsystematicforISRsimulation.
140,10 +10.1 +0.6 ±0.5 +4.0 +1.9 +15.6
An incorrect simulation of final state radiation (FSR) has a −10.3 −1.1 −5.6 −6.6 −17.2
negligible effect on the analysis’ acceptance. FSR can occur 140,20 +10.1 +1.2 ±1.0 +4.0 +0.4 +15.5
−10.3 −1.6 −3.9 −5.0 −16.2
in a prompt or displaced jet. But even if displaced, the extra 140,40 +10.1 +1.3 ±1.5 +6.3 +1.8 +16.5
jetcannotdegradetrackisolationordepositextraenergyinthe −10.3 −1.6 −4.6 −2.4 −15.8
ECaliftheπvhasdecayedintheHCal. 300,50 +9.6 +0.1 ±0.3 +9.0 +0.5 +13.9
−10.0 −0.3 −7.4 −3.0 −13.3
600,50 +11.2 +0.0 ±0.2 +11.7 +2.2 +17.0
7. Resultsandexclusionlimits −10.1 −0.1 −11.3 −4.4 −16.2
600,150 +11.2 +0.2 ±0.3 +11.5 +2.7 +17.5
−10.1 −0.2 −10.2 −5.3 −15.1
The global acceptance of the selected event topology in the
900,50 +12.8 +0.0 ±0.1 +12.6 +1.0 +18.5
signalMCsamplesisafunctionofmΦ,mπv andtheproperde- −11.5 −0.1 −9.7 −3.7 −15.9
cay length of the πv. At a proper decay length of 1.5 m the 900,150 +−1121..85 −+00..32 ±0.2 +−1110..89 −+20..59 +−1186..13
acceptance ranges from 0.07% to 0.61%. The main efficiency
lossisduetothelowprobabilitythatbothπ decayinsidethe
v
calorimeter. High mass samples suffer further efficiency loss
due to the Emiss requirement. Table 3 lists the expected num-
T
theprobabilityforthegivenobservationtobecompatiblewith
ber of events from all signal MC samples and the background
expectation in 20.3 fb−1. The m =126 GeV mass samples thesignal+backgroundhypothesis.
H
TheacceptanceisafunctionoftheΦmass,theπ massand
use the SM Higgs boson cross-sections of σ = 19.0 pb for v
SM
π proper decay length. To extrapolate to the number of ex-
thegluonfusionprocess: otherproductionmodesareignored. v
pectedeventsatdifferentproperdecaylengths,alargesample
The number of events observed in data, 24, is also shown for
ofπ decaysisgeneratedinarangefrom0to50mandanef-
comparison.Noexcessofeventsisobservedsincetheexpected v
ficiencymapasafunctionofπ boostisusedtodeterminethe
backgroundis23.5±8.0.TheCL method[31]isusedtoderive v
s
efficiency at each decay length. The resulting efficiencies are
an upper limit on the σ(Φ)×BR(Φ→π π ). A profile likeli-
v v
thenconvertedintothefinalnumberofexpectedeventsshown
hoodratioisusedastheteststatisticandafrequentestcalculator
inFig.4. Finally,Fig.5andFig.6showtheobservedlimitdis-
isusedtogeneratetoydata. ThelikelihoodincludesaPoisson
tributionforthethree126GeVHiggssamplesandfortheother
probabilitytermdescribingthetotalnumberofobservedevents.
Φsamplesrespectively.Thederived95%confidencelevel(CL)
Systematic uncertainties are incorporated as nuisance parame-
excludedrangesofproperdecaylengtharelistedinTable4for
ters through their effect on the mean of the Poisson functions
them =126GeVsamples,underthealternativeassumptions
andthroughconvolutionwiththeirassumedGaussiandistribu- H
ofa30%BRora10%BRforH→π π .
tions.ThenumberofexpectedeventsinsignalMCsamples,to- v v
getherwiththeestimateofexpectedbackground,theobserved
collision events and all the systematic uncertainties are pro-
vided as input for computing theCL value, which represents
s
7
Table3:Summaryofexpectednumberofsignalevents,expectedbackground
presentinthedatasample,andtheobservednumberofeventsin20.3fb−1.
Theglobalacceptanceisalsogiven. Theerroronthesignalsamplesisstatis-
ticalonly,theerrorontheexpectedbackgroundisstatistical⊕systematic.All
resultsarenormalisedforaproperdecaylengthoftheπv of1.5m. A100%
branchingratioforΦhs→πvπvisassumed.
Sample Expected Global
(mH,mπv [GeV]) yields acceptance(%)
126,10 536±23 0.139±0.006
126,25 941±44 0.244±0.011
126,40 365±31 0.095±0.008
-1n 20.3 fb 103 ATLAS Simulation (cid:242) L dt =s 2=0 8.3 T febV-1 Sample Expected Global
nts i (mH,mπv [GeV]) yields acceptance(%)
e
ev 100,10 440±29 0.073±0.005
d
ecte 100,25 424±37 0.070±0.006
Exp 102 140,10 525±20 0.168±0.006
140,20 900±37 0.287±0.012
140,40 641±30 0.205±0.010
300,50 444±11 0.609±0.015
mmmHHH 111222666 GGGeeeVVV --- mmmpppvvv 111000 GGGeeeVVV 600,50 35±1 0.330±0.010
10 mmmHHH 111222666 GGGeeeVVV --- mmmpppvvv 222555 GGGeeeVVV 600,150 41±2 0.386±0.015
mmmFFF 111444000 GGGeeeVVV --- mmmpppvvv 444000 GGGeeeVVV 900,50 3.5±0.1 0.304±0.011
10-1 1 10 900,150 4.6±0.2 0.397±0.016
p proper decay length [m]
v
Background Expectedevents
(a)
SMMulti-jets 23.2±8.0
Cosmicrays 0.3±0.2
-1b TotalExpectedBackground 23.5±8.0
0.3 f ATLAS mmmFFF 333000000 GGGeeeVVV --- mmmpppvvv 555000 GGGeeeVVV Data 24
events in 2 103 S(cid:242) Lim dt u= 2la0.t3i fob-n1 mmmmmmFFFFFF 696969000000000000 GGGGGGeeeeeeVVVVVV ------ mmmmmmppppppvvvvvv 1515155050500 0 0 GGG GGGeeeeVeVeVVVV
Expected 102 s = 8 TeV s ×BR / SM 1 ATLAS
(cid:242)
sn L dt = 20.3 fb-1
o
mit s = 8 TeV
er Li BR 30%
p
10 Up
L
% C 10-1 BR 10%
5
9
10-1 1 10
p proper decay length [m]
v mmmHHH 111222666 GGGeeeVVV --- mmmpppvvv 111000 GGGeeeVVV
mmmHHH 111222666 GGGeeeVVV --- mmmpppvvv 222555 GGGeeeVVV
(b)
mmmHHH 111222666 GGGeeeVVV --- mmmpppvvv 444000 GGGeeeVVV
10-2
10-1 1 10
Fig.4:Numberofeventsexpectedtopasstheanalysisselectionin20.3fb−1as p proper decay length [m]
v
afunctionoftheπvproperdecaylengthfor(a)threelow-massdatasetsand(b)
threehigh-massdatasets.100%branchingratiosforΦhs→πvπvareassumed.
Fig.5:Observed95%CLlimitsonσ/σSMformH=126GeVasafunctionof
theπvproperdecaylength:thesolidlineisformπv=10GeV,theshort-dashed
lineisformπv=25GeV,thelong-dashedlineisformπv=40GeV.TheσSM
istakentobe19.0pb.ThehorizontalsolidlinecorrespondstoBR=30%and
thehorizontaldashedlinetoBR=10%.
8
No significant excess of events is observed over the back-
b] 102
·smit on BR [p 10 mmmmmmmmmmmmmmmmmmmmmmmmmFFFFFFFFFFFFFFFFFFFFFFFFF 111111111111111111111111100444004440044400444004440000000000000000000000000 GGGGGGGGGGGGGGGGGGGGGGGGGeeeeeeeeeeeeeeeeeeeeeeeeeVVVVVVVVVVVVVVVVVVVVVVVVV ------------------------- mmmmmmmmmmmmmmmmmmmmmmmmmpppppppppppppppppppppppppvvvvvvvvvvvvvvvvvvvvvvvvv 12124121241212412124121240500005000050000500005000 GGGGGGGGGGGGGGGGGGGGGGGGGeeeeeeeeeeeeeeeeeeeeeeeeeVVVVVVVVVVVVVVVVVVVVVVVVV fH1go8rirog.5udg0nisfdfmdeeersceatansiysmtuisnamctgaeiln.taogLrπbiamvo3spi0tors%onapareBenrdRsdeπetacvroaemnyraltuehslnseegdcπtohvomsuptbbr,oeinatpwanetdreioedbnneesct0.wa.F1yeo0elrenmna0gSa.tn1Mhd4s
Li
er mand8.32massumingaBRof10%. ResultsforlowmassΦ
p
Up (100GeVand140GeV)andhighmassΦ(300GeV,600GeV,
L
% C and900GeV)havealsobeenpresentedasafunctionofproper
95 1 decaylength.
ATLAS
(cid:242)
L dt = 20.3 fb-1 Acknowledgements
s = 8 TeV
10-1 We thank CERN for the very successful operation of the
10-1 1 10
p proper decay length [m] LHC,aswellasthesupportstafffromourinstitutionswithout
v
whomATLAScouldnotbeoperatedefficiently.
(a) Observed95%CLlimitsformΦ=100and140GeV. We acknowledge the support of ANPCyT, Argentina; Yer-
PhI, Armenia; ARC, Australia; BMWFW and FWF, Austria;
ANAS,Azerbaijan;SSTC,Belarus;CNPqandFAPESP,Brazil;
b]
p
R [ mmmmmFFFFF 333330000000000 GGGGGeeeeeVVVVV ----- mmmmmpppppvvvvv 5555500000 GGGGGeeeeeVVVVV NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile;
B mmmmmFFFFF 666660000000000 GGGGGeeeeeVVVVV ----- mmmmmpppppvvvvv 5555500000 GGGGGeeeeeVVVVV CAS, MOST and NSFC, China; COLCIENCIAS, Colom-
· mmmmmFFFFF 666660000000000 GGGGGeeeeeVVVVV ----- mmmmmpppppvvvvv 111115555500000 GGGGGeeeeeVVVVV
son 10 mmmmmFFFFF 999990000000000 GGGGGeeeeeVVVVV ----- mmmmmpppppvvvvv 5555500000 GGGGGeeeeeVVVVV bia; MSMT CR, MPO CR and VSC CR, Czech Repub-
mit mmmmmFFFFF 999990000000000 GGGGGeeeeeVVVVV ----- mmmmmpppppvvvvv 111115555500000 GGGGGeeeeeVVVVV lic; DNRF, DNSRC and Lundbeck Foundation, Denmark;
Li
er EPLANET, ERC and NSRF, European Union; IN2P3-CNRS,
p
p
L U CEA-DSM/IRFU,France;GNSF,Georgia;BMBF,DFG,HGF,
% C 1 MPG and AvH Foundation, Germany; GSRT and NSRF,
5
9 Greece; RGC,HongKongSAR,China; ISF,MINERVA,GIF,
ATLAS
I-COREandBenoziyoCenter,Israel;INFN,Italy;MEXTand
(cid:242)
L dt = 20.3 fb-1 JSPS,Japan;CNRST,Morocco;FOMandNWO,Netherlands;
10-1 s = 8 TeV BRFandRCN,Norway;MNiSWandNCN,Poland;GRICES
and FCT, Portugal; MNE/IFA, Romania; MES of Russia and
10-1 1 10
p proper decay length [m] ROSATOM,RussianFederation;JINR;MSTD,Serbia;MSSR,
v
Slovakia;ARRSandMIZSˇ,Slovenia;DST/NRF,SouthAfrica;
(b) Observed95%CLlimitsformΦ=300,600,and900GeV. MINECO, Spain; SRC and Wallenberg Foundation, Sweden;
SER, SNSF and Cantons of Bern and Geneva, Switzerland;
Fig.6:Observed95%CLlimitsonσ×BR[pb]for(a)lowand(b)high-mass NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and
Φsamples. Leverhulme Trust, United Kingdom; DOE and NSF, United
StatesofAmerica.
Table4: Rangesofπvproperdecaylengthsexcludedat95%CLassuminga The crucial computing support from all WLCG partners is
30%anda10%BRforamH=126GeV.
acknowledged gratefully, in particular from CERN and the
MCsample Excludedrange Excludedrange ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Den-
m ,m 30%BRH→π π 10%BRH→π π mark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA
H πv v v v v
[GeV] [m] [m] (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC
126,10 0.10–6.08 0.14–3.13 (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA) and in
theTier-2facilitiesworldwide.
126,25 0.30–14.99 0.41–7.57
126,40 0.68–18.50 1.03–8.32
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