Search for new physics with dijet angular distributions in proton-proton collisions at sqrt(s)

34 Pages·2017·0.46 MB·English

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-EP/2017-047
2017/03/29
CMS-EXO-15-009
Search for new physics with dijet angular distributions in
√
proton-proton collisions at s = 13TeV
7
1
0 The CMS Collaboration∗
2

r
a
M

9
2 Abstract

]
x
e A search is presented for extra spatial dimensions, quantum black holes, and quark
-
p contact inter√actions in measurements of dijet angular distributions in proton-proton
e collisionsat s = 13TeV. ThedatawerecollectedwiththeCMSdetectorattheLHC
h and correspond to an integrated luminosity of 2.6fb−1. The distributions are found
[
to be in agreement with predictions from perturbative quantum chromodynamics
7
that include electroweak corrections. Limits for different contact interaction models
4
7 areobtainedinabenchmarkmodel,validtonext-to-leadingorderinQCD,inwhich
7 only left-handed quarks participate, with quark contact interactions excluded up to
4
a scale of 11.5 or 14.7TeV for destructive or constructive interference, respectively.
8
1 The production of quantum black holes is excluded for masses below 7.8 or 5.3TeV,
t/ dependingonthemodel. Thelowerlimitsforthescalesofvirtualgravitonexchange
i
m in the Arkani-Hamed–Dimopoulos–Dvali model of extra spatial dimensions are in
b therange7.9–11.2TeV,andarethemoststringentsetoflimitsavailable.
u
s
:
v
SubmittedtotheJournalofHighEnergyPhysics
i
X
r
a
(cid:13)c 2017CERNforthebenefitoftheCMSCollaboration.CC-BY-3.0license
∗SeeAppendixAforthelistofcollaborationmembers

1
1 Introduction
In the standard model (SM), pointlike parton-parton scattering in high energy proton-proton
collisions can give rise to dijet events, containing at least two jets with large transverse mo-
menta(p ). Sucheventsmaybeusedtotesttheperturbativepredictionsofquantumchromo-
T
dynamics(QCD)andtosearchforsignaturesofnewphysics(NP),suchasquarksubstructure
or compositeness [1–3], as well as for additional compactified large spatial dimensions [4, 5],
andquantumblackholes[6–8].
Theangulardistributionofdijetswithrespecttothebeamdirectionissensitivetothedynam-
ics of the scattering process, yet is not strongly dependent on the parton distribution func-
tions (PDFs), since the angular distributions of the dominant underlying processes, qg → qg,
qq(q(cid:48)) → qq(q(cid:48)), and gq → gg, are similar [9]. The dijet angular distribution is typically
expressed in terms of χ = exp[|(y −y )|], where y and y are the rapidities of the two
dijet 1 2 1 2
jets with highest p (the leading jets). The choice of this variable is motivated by the fact that
T
theχ distributionisuniforminRutherfordscattering,andpermitssignaturesfromNPthat
dijet
havemore-isotropicscattering-angledistributionsthanQCDprocessestobemoreeasilyiden-
tifiedandexaminedastheycouldproduceanexcessofeventsatlowvaluesofχ .
dijet
Acommonsignatureofquarkcompositenessmodelsistheappearanceofnewinteractionsbe-
Λ
tweenquarkconstituentsatacharacteristicscale, ,thatismuchlargerthanthequarkmasses.
Λ
At energies well below , these interactions are approximated through contact interactions
(CI) characterized by four-fermion couplings. The most stringent limits on quark CI come
from searches studying dijet angular distributions at high dijet invariant masses (M ) [10–12],
jj
andinclusivejet p distributions[13]. AprevioussearchperformedbytheCMSCollaboration
T √
attheCERNLHCat s = 8TeVusingdijetangulardistributions[11]providedlowerlimitson
Λ
rangingfrom8.8to15.2TeV,foravarietyofCImodels.
TheArkani-Hamed–Dimopoulos–Dvali(ADD)model[4,5]ofcompactifiedlargeextradimen-
sions (ED) provides a possible solution to the SM hierarchy problem. In proton-proton col-
lisions at the LHC, the ADD model predicts signatures of virtual graviton exchange that re-
sultinanonresonantenhancementofdijetproductionandanangulardistributionthatdiffers
from the QCD expectation. Signatures from virtual graviton exchange have previously been
sought at the LHC in dilepton [14–17], diphoton [18–20], and dijet [11, 21] final states, and
the most stringent limits on the cutoff scale come from the dijet angular analysis of CMS at
√
s = 8TeV [11] that range from 5.9 to 8.4TeV, depending on the model of virtual graviton
exchange.
In models with large ED, the fundamental Planck scale can be comparable to the electroweak
scale, which can make black hole production possible at the LHC [22–26]. Semiclassical black
holes that have masses much larger than the Planck scale and decay into multijets through
Hawkingradiation[27],havepreviouslybeensoughtinmultijetfinalstates[28–32]. Quantum
blackholes(QBH),producedwithmassclosetothereducedPlanckscale,decaypredominantly
intodijetsthatcanbestudiedusingdijetangulardistributions[6–8]. RecentsearchesforQBH
in dijet final states at the LHC are reported in Refs. [10, 12, 29, 30, 33–35]. Lower bounds on
√
QBH masses published by the CMS Collaboration at s = 8TeV range from 5.0 to 6.3TeV for
differentQBHmodels[34].
Measurements of dijet angular distributions at the SppS by the UA1 Collaboration [36], at the
Fermilab Tevatron by the D0 [37, 38] and CDF [39] Collaborations, and at the LHC by the
ATLAS [12, 35, 40–42] and CMS [11, 43–45] Collaborations have previously been reported. In
√
thispaper,theearliersearchesbyCMS[11,44,45]at s = 7and8TeVareextendedtohigher
2 2 TheCMSdetectorandeventselection
√
M usingdatathatcorrespondtoanintegratedluminosityof2.6fb−1at s = 13TeV,following
jj
thesameanalysisstrategyreportedbythepreviouspublications. Themeasurementofthedijet
angular distributions, unfolded for detector effects, is presented and is then analyzed for the
presenceofcontactinteractions,largeextradimensions,andquantumblackholes.
2 The CMS detector and event selection
TheCMSapparatusisbasedonasuperconductingsolenoidof6minternaldiameter,providing
an axial field of 3.8T. Within the solenoid and nearest to the interaction point are the silicon
pixelandstriptrackers. Surroundingthetrackervolumearetheleadtungstatecrystalelectro-
magnetic calorimeter and the brass and scintillator hadron calorimeter. The pixel and tracker
cover a pseudorapidity region of |η| < 2.5 while the calorimeters cover |η| < 3.0. In addi-
tion,CMShasextensiveforwardcalorimetry,whichextendsthecoverageto|η| < 5.0. Finally,
muonsaremeasuredingas-ionizationdetectorsembeddedinthesteelflux-returnyokeofthe
solenoid, with a coverage of |η| < 2.4. A more detailed description of the CMS detector, to-
gether with a definition of the coordinate system used and the relevant kinematic variables,
canbefoundinRef.[46].
Events are reconstructed using the particle-flow algorithm [47, 48] to identify and reconstruct
individualparticlesfromeachcollisionbycombininginformationfromallCMSsubdetectors.
Identifiedparticlesincludechargedhadrons,neutralhadrons,electrons,muons,andphotons.
The particles are clustered into jets using the anti-k algorithm [49] with a jet size parameter
T
R = 0.4. The jet energies are corrected for the combined response function of the calorimeters
usingcorrectionsderivedfromdataandMonteCarlo(MC)simulations[50]. Tocomparedata
with next-to-leading order (NLO) and PYTHIA 8.212 [51, 52] predictions, particle-level jets are
reconstructed by applying the same jet clustering algorithm to the four-vectors of generated
stableparticles(lifetime cτ > 1cm)inthecaseof PYTHIA8, andtotheoutgoingpartonsinthe
caseofNLOpredictions.
A two-tiered system, consisting of the level-1 (L1) and high-level (HLT) triggers, is used by
CMS to record events of interest [53]. The selection criteria for this analysis are based upon
thescalarsumofthetransversemomentaofthejetsreconstructedbytheL1andHLTsystems.
Theselectionthresholdwasvariedoverthecourseofthedatatakingandwasbetween100and
175GeVatL1andbetween650and800GeVatHLT.
Intheofflineeventselection,eventswithatleasttworeconstructedjetsareselected. Spurious
jetsfromnoiseornon-collidingbackgroundsarerejectedbyapplyingloosequalitycriteria[54]
to jet properties. For each event a reconstructed primary vertex [55] is required to lie within
±24cmofthedetectorcenteralongthebeamlineandwithin2cmofthedetectorcenterinthe
planetransversetothebeam. Theprimaryvertexisdefinedasthevertexwiththehighestsum
ofsquaresofallassociatedchargedparticletransversemomenta.
ThetwoleadingjetsareusedtomeasurethedijetangulardistributionsinseveralregionsofM
jj
whichare,inunitsofTeV,1.9–2.4,2.4–3.0,3.0–3.6,3.6–4.2,4.2–4.8,and>4.8. Thehighestthree
M rangeswerechosentomaximizetheexpectedsensitivitytotheNPsignalsconsidered. The
jj
phase space for this analysis is defined by selecting events with 1 ≤ χ < 16 and |y | <
dijet boost
1.11,wherey = (1/2)(y +y ). Thisselectionrestrictstherapidities|y |and|y |ofthetwo
boost 1 2 1 2
highest-p jetstobelessthan2.5andtheir p tobelargerthan200GeV. Thetriggerefficiency
T T
exceeds 99% over the entire phase space. The highest value of M observed in the data is
jj
6.8TeV.
3
3 Unfolding and experimental uncertainties
Fluctuationsinjetresponsefromthejet p resolutionofthedetectorcancauselow-energyjets
T
tobemisidentifiedasleadingjets. Suchfluctuationscanproducebin-to-binmigrationsinboth
χ and M . The measured distributions are corrected for these migrations and unfolded to
dijet jj
theparticlelevelusingtheD’Agostiniiterationmethod[56]implementedinthe ROOUNFOLD
package[57]. Theunfoldingcorrectionsaredeterminedusingatwo-dimensionalresponsema-
trixmappingthegenerator-levelM andχ distributionsontothemeasuredvalues. Thisma-
jj dijet
trixisobtainedusingparticle-leveljetsfromthePYTHIA8MCeventgeneratorthataresmeared
in p using a double-sided Crystal-Ball parameterization [58] of the response. This parame-
T
terization takes into account the full jet energy resolution including non-Gaussian tails. The
unfoldingcorrectionschangetheshapeofthedijetangulardistributionsbylessthan1%across
χ inthelowest M range,andbylessthan5%acrossχ inthehighest M range.
dijet jj dijet jj
Thedijetangulardistributionsarenormalizedtotheintegrateddijetcrosssectionsineach M
jj
range, denoted (1/σ )(dσ /dχ ), where σ is the cross section in the analysis phase
dijet dijet dijet dijet
spaceconsidered. Thenormalizedangulardistributionsarerelativelyinsensitivetomanysys-
tematiceffects. Themainsystematicuncertaintiescomefromthejetenergyscale,thejetenergy
resolution,andtheunfoldingcorrection. Theeffectsoftheseuncertaintiesonthedijetangular
distributionsaredescribedbelow.
The maximum jet energy scale uncertainty is less than 1% and has a dependence on η of less
than 1% per unit of η [50, 59] in the phase space of the analysis. The resulting uncertainty in
the χ distributionsduetothejetenergycalibrationuncertaintiesisfoundtobe2.2%inthe
dijet
lowest M rangeand3.6%inthehighest M range,overallχ bins.
jj jj dijet
ThejetenergyresolutionuncertaintyisevaluatedbychangingthewidthoftheGaussiancoreof
theCrystal-Ballparameterizationoftheresponsebyupto±10%[50,59],dependinguponthe
jet η, and comparing the resultant unfolded distributions before and after these changes. This
uncertaintyisfoundtobelessthan1.1%. Thesystematicuncertaintyfromthemodellingofthe
tails of the jet resolution is evaluated using a Gaussian function to parameterize the response,
and assigning as an uncertainty half of the difference between the unfolded distributions de-
terminedfromthisGaussianansatzandthenominalcorrection. Thesizeofthisuncertaintyis
lessthan1%.
A source of uncertainty to the unfolding correction arises from the use of a parameterized
modeltosimulatethejet p resolutionofthedetector. Thisuncertaintyisestimatedbycompar-
T
ingthesmeared χ distributionstotheonesfromadetailedsimulationoftheCMSdetector
dijet
using GEANT4 [60], and is found to be less than 1% in all Mjj ranges. An additional system-
atic uncertainty is evaluated to account for mismodelling of the dijet kinematic distributions
byapplyingtheunfoldingcorrectionsdeterminedwithPYTHIA8tosmearedχdijetdistributions
from MADGRAPH5 aMC@NLO 2.2.2 [61], and comparing the results with the generated χdijet
distributions. Thisuncertaintyisfoundtobelessthan1%forall M .
jj
The effect of additional interactions in the same or adjacent proton bunch crossings (pileup)
relative to the interaction of interest is studied by comparing χ distributions in simulated
dijet
sampleswherethedistributionofpileupinteractionsisvariedaccordingtoitsuncertainty. The
effectofthisvariationontheχ distributionsisobservedtobelessthan1%.
dijet
AsummaryoftheleadingexperimentalsystematicuncertaintiesisprovidedinTable1. Though
inthesubsequentanalysisofthedatatheuncertaintiesaretreatedseparately,fordisplayinTa-
ble1andinthefiguresthetotalexperimentalsystematicuncertaintyinthe χ distributions
dijet
iscalculatedasthequadraticsumofthecontributionsduetotheuncertaintiesinthejetenergy
4 4 Theoreticalpredictionanduncertainties
Table 1: Summary of main experimental and theoretical uncertainties in the normalized χ
dijet
distributions. Althoughthechangeintheχ distributionfromeachuncertaintyistakeninto
dijet
account in the statistical analysis, this table summarizes the uncertainty in just the smallest
χ bin, for the smallest and largest bins in dijet mass. The uncertainty in the dijet bin with
dijet
largest mass is dominated by the statistical experimental contribution, while the theoretical
contributionisdominatedbytheuncertaintyintheNLOQCDscale.
Uncertainty 1.9 < M < 2.4TeV M > 4.8TeV
jj jj
Statistical 1.1% 26%
Jetenergyscale 2.2% 3.6%
Jetenergyresolution(core) 0.4% 1.1%
Jetenergyresolution(tails) 0.6% 0.5%
Unfolding,modelling 0.1% 0.8%
Unfolding,detectorsimulation 0.3% 0.8%
Pileup 0.2% 0.2%
Totalexperimental 2.6% 26%
NLOQCDscale +7.9% +13%
−2.8% −4.9%
PDF(CT14eigenvectors) 0.15% 0.4%
Nonperturbativeeffects <1% <1%
Totaltheoretical +7.9% +13%
−2.8% −4.9%
calibration,jet p resolution,unfoldingcorrection,andpileup.
T
4 Theoretical prediction and uncertainties
We compare the measured normalized dijet angular distributions with the predictions of per-
turbative QCD at NLO, which are made with NLOJET++ 4.1.3 [62] in the FASTNLO 2.1 frame-
work [63]. With the inclusion of the electroweak (EW) corrections for dijet production [64],
the predictions of the normalized χ distributions are corrected up to 1% and up to 5% at
dijet
small and large M , respectively. The factorization (µ ) and renormalization (µ ) scales are set
jj f r
totheaverage p ofthetwojets, (cid:104)p (cid:105),andthePDFsaretakenfromtheCT14set[65]. Theuse
T T
of a more flexible statistical combination of multiple PDF sets as in PDF4LHC15 100 [65–70]
exhibited only small differences as compared to the use of the CT14 PDF set alone, and had
negligibleimpactontheCIlimitsdescribedinthenextsection.
WeevaluatedtheimpactontheQCDpredictionsofnonperturbativeeffectsrelatedtohadron-
izationandmultiplepartoninteractionsusingPYTHIA8withtheCUETP8M1tune[71,72]and
HERWIG++ 2.7.1 [73] with tune EE5C. The effects are found to be negligible in both MC event
generators. Wecanthereforecomparethedatacorrectedtoparticle-levelwiththeparton-level
theorypredictions.
The choices of the µ and µ scales dominate the uncertainties in the QCD prediction. These
f r
uncertainties are evaluated following the proposal in Refs. [74, 75] by changing the default
choice of scales in the following 6 combinations: (µ /(cid:104)p (cid:105), µ /(cid:104)p (cid:105)) = (1/2,1/2), (1/2,1),
f T r T
(1,1/2), (2,2), (2,1),and(1,2). Thesechangesmodifythepredictionsofthenormalizedχ
dijet
distributions by up to 8% and up to 13% at small and large values of M , respectively. The
jj
uncertainty due to the choice of PDFs is determined from the 28 eigenvectors of CT14 using
theproceduredescribedinRef.[76],andisfoundtobelessthan0.15%atlow M andlessthan
jj
0.4% at high M . The uncertainty of the strong coupling constant has a negligible impact on
jj
5
the normalised χ distribution. A summary of the leading systematic uncertainties in the
dijet
theoreticalpredictionsisalsogiveninTable1.
NewphysicssignaturesfromCIswithflavor-diagonalcolor-singletcouplingsbetweenquarks
arestudied. ThesearedescribedbytheeffectiveLagrangian[2,3]:
L = 2π (cid:2)η (q γµq )(q γ q )+η (q γµq )(q γ q )+2η (q γµq )(q γ q )(cid:3),
qq Λ2 LL L L L µ L RR R R R µ R RL R R L µ L
where the subscripts L and R refer to the left and right chiral projections of the quark fields,
respectively, and η , η , and η aregiventhevaluesof0, +1, or −1. Thevariouscombina-
LL RR RL
tions of (η , η , η ) correspond to different CI models. The following CI possibilities with
LL RR RL
color-singletcouplingsamongquarksareinvestigated:
Λ (η , η , η )
LL RR RL
Λ± (±1, 0, 0)
LL
Λ± ( 0,±1, 0)
RR
Λ± (±1,±1,±1)
VV
Λ± (±1,±1,∓1)
AA
Λ± ( 0, 0,±1)
(V−A)
The models with positive (negative) η or η lead to destructive (constructive) interference
LL RR
withtheQCDterms,andalower(higher)crosssection,respectively. InallCImodelsdiscussed
in this paper, NLO QCD corrections are employed to calculate the cross sections. In proton-
Λ± Λ±
protoncollisionsthe and modelsresultinidenticaltreelevelcrosssectionsandNLO
LL RR
Λ± Λ±
corrections, and consequently lead to the same sensitivity. For and , as well as for
VV AA
Λ±
,theCIpredictionsareidenticalattreelevel,butexhibitdifferentNLOcorrectionsand
(V−A)
yielddifferentsensitivity. ForcalculatingtheCIterms,aswellastheinterferencebetweenthe
CItermsandQCDtermsatleadingorder(LO)andNLOinQCD,theCIJET1.0program[77]is
employed.
FortheADDmodel,twoparameterizationsforvirtualgravitonexchangeareconsidered,Giudice–
Rattazzi–Wells (GRW) [78] and Han–Lykken–Zhang (HLZ) [79]. In the GRW convention, the
sum over the Kaluza–Klein graviton excitations in the effective field theory is regulated by a
Λ
single cutoff parameter . In the HLZ convention, the effective theory is described in terms
T
of two parameters, the cutoff scale M and the number of extra spatial dimensions n . The
S ED
parameters M andn aredirectlyrelatedtoΛ [80]. Weconsidermodelswith2–6EDs. The
S ED T
case of n = 1 is not considered since it would require an ED of the size of the order of the
ED
solar system; the gravitational potential at these distances would be noticeably modified and
this case is therefore excluded by observation. The case of nED = 2 is special in the sense t√hat
therelationbetween M andΛ alsodependsontheparton-partoncenter-of-massenergy sˆ.
S T
TheADDpredictionsarecalculatedwithPYTHIA8.
Quantum black hole production is studied within the framework of the ADD model with
n = 6, and the Randall–Sundrum model with n = 1 (RS1) [81, 82]. In these models, the
ED ED
QBH production cross section is typically described by the classical geometrical cross section
σ ≈ πr2,wherer istheSchwarzschildradiusoftheblackhole. TheSchwarzschildradius
QBH s s
dependsonthemassoftheQBH,thePlanckscale(M ),andthenumberofspatialdimensions.
P
Since QBHs are produced with mass threshold close to the Planck scale, we set the minimum
quantumblackholemass MQBH equalto MP forsimplicity. The QBH 3.0generator[83]isused
forthepredictions.
6 6 Summary
To take into account the NLO QCD and EW corrections to SM dijet production when probing
the ADD and QBH models, the cross section difference σQCD −σQCD is evaluated for
NLO+EWcorr LO
each M and χ bin and added to the ADD and QBH predictions. This procedure provides
jj dijet
an SM+ADD or SM+QBH prediction wherein the QCD terms are corrected to NLO with EW
corrections while the ADD or QBH terms are calculated at LO. In all the predictions, changes
from theoretical uncertainties associated with scales and PDFs are applied only to the QCD
prediction,therebytreatingtheeffectiveNPtermsasfixedbenchmarkterms.
5 Results
Thenormalizedχ distributionsforallmassbinsarecomparedtoNLOpredictionswithEW
dijet
correctionsinFig.1. Nosignificantdeviationfromthetheoryisobserved. Thedistributionsare
alsocomparedtopredictionsforQCD+CIwithΛ+ = 11TeV,QCD+ADDwithΛ (GRW) =
LL T
10TeV, and QCD+QBH with M (n = 6ADD) = 7.5TeV. The QCD+ADD Λ (GRW) =
QBH ED T
10TeV prediction corresponds to QCD+ADD M (HLZ) = 10.1, 11.9, 10.0, 9.9 and 8.4TeV for
S
n = 2, 3, 4, 5 and 6, respectively. The signal distributions are shown only for the highest
ED
threerangesof M ,sincethosebinsdominatethesensitivitytotheNPsignalsconsidered. An
jj
expanded version of the normalized χ distributions in the highest three ranges of M is
dijet jj
showninFig.2. Themeasuredχ distributionsareusedtodetermineexclusionlimitsonthe
dijet
NPmodels.
Λ
A modified frequentist approach [84, 85] is used to set exclusion limits on the scale . The
log-likelihoods L and L aredefinedfortherespectiveQCD-onlyandQCD+NPhy-
QCD QCD+NP
potheses as a product of Poissonian likelihood functions for each bin in χ for the highest
dijet
three ranges of M . The predictions for each M range are normalized to the number of ob-
jj jj
served events in that range. The p-values for the two hypotheses, P (q ≥ q ) and
QCD+NP obs
P (q ≤ q ),arebasedonthelog-likelihoodratioq = −2ln(L /L ). Theyareeval-
QCD obs QCD+NP QCD
uatedbygeneratingdistributionsofqusingensemblesofpseudo-experiments,wheresystem-
atic uncertainties are represented as Gaussian-constraint nuisance parameters and are treated
according to the frequentist paradigm [86]. Limits on the QCD+NP models are set based on
thequantityCL = P (q ≥ q )/(1−P (q ≤ q )),whichisrequiredtobelessthan
s QCD+NP obs QCD obs
0.05foranexclusionat95%confidencelevel(CL).Theobservedandexpectedexclusionlimits
ondifferentCI,ADD,andQBHmodelsobtainedinthisanalysisat95%CLarelistedinTable2.
The observed limits are smaller than the expected limits owing to a slight excess of events in
the lowest χ bin in the 3.6–4.2TeV mass bin. The limits on M for the different numbers of
dijet S
extradimensions, n ,directlyfollowfromthelimitforΛ . ThelimitsfortheCIscaleΛ+
ED T LL/RR
arealsodeterminedforthecaseinwhichthedataarenotcorrectedfordetectoreffects,andare
foundtoagreewiththequotedoneswithin3%.
TheagreementofthedatawithQCDpredictionsisquantifiedbycalculatingP (q ≤ q )as
QCD obs
described above. The largest excess is found in the 3.6–4.2TeV mass bin with a significance of
1.8standarddeviations.
6 Summary
√
Normalized dijet angular distributions have been measured at s = 13TeV with the CMS
detectoroverawiderangeofdijetinvariantmasses. Thedistributionsarefoundtobeinagree-
ment with predictions of perturbative QCD and are used to set lower limits on the contact-
interaction scale for a variety of quark-compositeness models that include next-to-leading or-
7
2.7 fb-1 (13 TeV)
et
dij 0.2 CMS MQBH (nED = 6 ADD) = 7.5 TeV
cd L + (CI) = 11 TeV
/ Data LL
dijet 0.15 NLO QCD+EW L T (GRW) = 10 TeV
sd
0.1

et Mjj > 4.8 TeV
dij
0.05
s/
1
0.1 2 4 6 8 10 12 14 c 16
4.2 < M < 4.8 TeV dijet
jj
0.05
0.1 2 4 6 8 10 12 14 cdij1et6
3.6 < M < 4.2 TeV
jj
0.05
0.1 2 4 6 8 10 12 14 cdij1et6
3.0 < M < 3.6 TeV
jj
0.05
0.1 2 4 6 8 10 12 14 cdij1et6
2.4 < M < 3.0 TeV
jj
0.05
0.1 2 4 6 8 10 12 14 cdij1et6
1.9 < M < 2.4 TeV
jj
0.05
2 4 6 8 10 12 14 16
c
dijet
√
Figure 1: Normalized χ distributions for 2.6 fb−1 of integrated luminosity at s = 13TeV.
dijet
The corrected distributions in data are compared to NLO predictions (black dotted line). The
verticalbaroneachdatapointrepresentsstatisticalandsystematicexperimentaluncertainties
combinedinquadrature. Thehorizontalbarindicatesthebinwidth. Theoreticaluncertainties
areindicatedbythegraybands. AlsoshownarethepredictionsforQCD+QBHwith n = 6
ED
and M = 7.5TeV (green dashed-dotted line), QCD+CI with Λ+ = 11TeV (red solid line),
QBH LL
andQCD+ADDwithΛ (GRW) = 10TeV(bluedashedline).
T
8 6 Summary
2.7 fb-1 (13 TeV) 2.7 fb-1 (13 TeV)
dijet D ata CMS dijet D ata CMS
N LO QCD+EW N LO QCD+EW
cd cd
s/ ddijetdijet 0.2 MLLLL +L-L+V-QLLVB H((((CCCC (IInII))))E ====D 11=1111 116 TT TTAeeeeDVVVVD) = 7.5 TeV s/ ddijetdijet 0.2 MLLLL +L-L+V-QLLVB H((((CCCC (IInII))))E ====D 11=1111 116 TT TTAeeeeDVVVVD) = 7.5 TeV
0.15 VV 0.15 VV
s1/ L V-A (CI) = 11 TeV s1/ L V-A (CI) = 11 TeV
L (GRW) = 10 TeV L (GRW) = 10 TeV
T T
M > 4.8 TeV 4.2 < M < 4.8 TeV
jj jj
0.1 0.1
0.05 0.05
0 0
2 4 6 8 10 12 14c 16 2 4 6 8 10 12 14c 16
dijet dijet
2.7 fb-1 (13 TeV)
dijet D ata CMS
N LO QCD+EW
cd
s/ ddijetdijet 0.2 MLLLL +L-L+V-QLLVB H((((CCCC (IInII))))E ====D 11=1111 116 TT TTAeeeeDVVVVD) = 7.5 TeV
0.15 VV
s1/ L V-A (CI) = 11 TeV
L (GRW) = 10 TeV
T
3.6 < M < 4.2 TeV
jj
0.1
0.05
0
2 4 6 8 10 12 14c 16
dijet
Figure 2: Normalized χ distributions for 2.6 fb−1 of integrated luminosity in the highest
dijet
three mass bins. The corrected distributions in data are compared to NLO predictions with
non-perturbativecorrections(blackdottedline). Theverticalbaroneachdatapointrepresents
statistical and systematic experimental uncertainties combined in quadrature. The horizontal
bar indicates the bin width. Theoretical uncertainties are indicated by the gray band. Also
shownarethepredictionsforvariousQBH,CI,andADDmodels.