NEUTRINO PHYSICS WITH THE OPERA
EXPERIMENTGiovanni De Lellis
University “Federico II” and INFN Napoli
On behalf of the OPERA Collaboration

On	  behalf	  of	  the	  OPERA	  Collabora2on	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  1	  PHYSICS: FROM NEUTRINO MIXING TO OSCILLATIONS

3x3 Unitary Mixing Matrix

Amospheric ν, SuperK,
K2K, MINOS, T2K
OPERA

Chooz, Daya Bay, RENO, T2K,MINOS, NOvA. …

Δm232 = (2.50 ±0.04) 10-3 eV2
θ32= (45.8 ± 3.2)°	  θ13= (8.88 ± 0.39)°	  05/01/17

PDG 2016	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  Solar ν, Borex, SuperK,SNO, KamLAND, …
Δm221 = (7.37 ±0.16) 10-5 eV2
θ12= (33.4 ± 0.85)°	  2	  Back to 1998: Neutrino98, Takayama, Japan

T. Kajita
Nobel Laureate 2015
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  3	  

By T. Kajita

Current status
PRL 112 (2014) 181801

P = sin2 (2#) sin2

05/01/17	  ✓2m LE◆• ντ not yet seen in 1998!
• First indication of ντ in 2001at Fermilab (DONUT)

Giovanni	  De	  Lellis,	  KMI	  Symposium	  4	  THE OPERA EXPERIMENTFirst direct detection of νµ à ντ oscillations in appearance mode 	  • Super-Kamiokande (MACRO and Soudan-2) discoveryof oscillations with atmospheric neutrinos• Later confirmation with solar neutrinos and acceleratorbeams•

K2K, PRL 94 (2005) 081802
MINOS, PRL 97 (2006) 191801

An important, missing tile in the oscillation picture
CNGS (CERN to Gran Sasso) beam approved at CERN in December 1999

The PMNS 3-flavor oscillation formalism predicts:

P (⌫µ ! ⌫⌧ ) ⇠ sin2 2✓23 cos4 ✓13 sin2 ( m223 L/4E)

Requirements:	   1) Long baseline
2) High energy neutrinos
3) High intensity beam4) Detect short lived τ leptons

05/01/17

Giovanni	  De	  Lellis,	  KMI	  Symposium	  5	  THE PRINCIPLE:HYBRID DETECTOR WITH MODULAR STRUCTUREτ DECAY
CHANNEL

BR (%)

τ →µ17.7

τ →e

17.8

τ →h49.5

τ →3h15.0•･ Small neutrino cross-section and beam divergence: massive active target (~ 1.2 kton)•･ Detect τ-lepton production and decay: micrometric space resolution•･ Underground location (106 reduction of cosmic ray flux)•･ Electronic detectors to provide the“time stamp”, preselect the interaction brick andreconstruct µ charge/momentum
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  6	  THE OPERA COLLABORATION
160 physicists, 28 institutions in 11 countries

Belgium
IIHE-ULB Brussels

Croatia
IRB Zagreb

Italy
Bari
Bologna
Frascati,
LNGS
Naples
PadovaRome
SalernoRussia
INR RAS Moscow
LPI RAS Moscow
SINP MSU Moscow
JINR Dubna

Switzerland
BernFranceLAPP Annecy
IPHC Strasbourg

Germany
HamburgIsrael
Technion Haifa

Japan
Aichi
Toho
Kobe
NagoyaNihon

Turkey
METU, Ankara

Korea
Jinju

http://operaweb.lngs.infn.it
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  7	  OPERA-CNGS ROADMAPJULY 2008

2006
JULY AUGUST
2003

CNGS RUN

L = 732 km
Gran Sasso

CNGS RUN
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  8	  

CNGS BEAM AND LNGS SITE

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  9	  

CNGS BEAM
Tuned for ντ-appearance at LNGS

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  10	  LNGS OF INFN
The world largest underground physics laboratory• ~180 000 m3 caverns’ volume• ~3 100 m.w.e. overburden• ~1 cosmic µ / (m2 x hour)• experimental infrastructure suitable
to host detector and related facilities• caverns oriented towards CERN

OPERA
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  11	  The CNGS beam along its five years ofoperation 2008 ÷ 2012
Year Beam days
2008
2009
2010
2011
2012
Total

123
155
187
243
257
965

P.O.T.
(1019)
1.74
3.53
4.094.75
3.86
17.97

p.o.t. (1018)

2012	  2011	  2010	  2009	  2008	  date

Last neutrino interaction recorded on December 3rd 201205/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  12	  PHYSICS RESULTS

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  13	  COSMIC-RAY ANALYSIS	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  14	  Cosmic-muon rate and temperature dependence 	  • Gran Sasso underground ~ 3800 m w.e. à Minimum muonenergy ~ 1.8 TeV• Atmospheric temperature increase à density decrease à increase
the pion decay rate à muon rate increase Iµ (t) = Iµ0 +Iµ = Iµ0 +2⇡
Iµ cos(t t0 )TIµTe↵= ↵TIµ0Te↵

R1
T (x)W (x)dx
Tef f = 0 R 1W (x)dx0High W in high atmosphere à high energy muons

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  15	  Annual modulation of cosmic-muon rateIµ= (1.32 ± 0.11)%0Iµt0 = 216 ± 1605/01/17	  Giovanni	  Dfore	  Lellis,	  KMI	  Symposium	   Weather Forecasts (ECMWF)
16	  Temperature
data by the European Center
Medium-range

Muon rate vs temperature variations
muon rate

hRaY

1950

1900

Entries
MeanStd Dev
χ2 / ndf
Probc
Aphi

All data folded in one year	  441
180.1
103.6
382.3 / 362
0.22211783 ± 1.4
23.43 ± 1.95
195.1 ± 4.7

R = 0.42

1850

1800

1750

1700

1650
050

100

150

200

250

300

350
days

t0 = 195 ± 5Maximum on July 14thIµTe↵=↵TIµ0Te↵↵T = 0.93 ± 0.06
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  17	  OSCILLATION PHYSICS

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  18	  νµ→ντ ANALYSIS STRATEGY• 2008-2009 runs
– No kinematical selection: get confidence on the detector
performances before applying any kinematical cut– Slower analysis speed (signal/noise not optimal)– Kinematical selection applied for the candidate selection,
coherently for all runs
– Good data/MC agreement shown• 2010-2012 runs
– Pµ < 15 GeV/c, to suppress charm background– Prioritise the analysis of the most probable brick in the probability
map: optimal ratio between efficiency and analysis time
– Analyse the other bricks in the probability map
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  19	  CHARMED HADRON PRODUCTION
control sample for the τ search
to check the efficiency à signal expectation
νµµ−

W+cd, s05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  20	  CHARMED HADRON PRODUCTION
•
•
•
•
•

Charm and τ decays have the same topology
Similar lifetime and masses
Charmed hadrons from νµ CC interactions
Muon at the primary vertex
Used as “control sample”

Background fromhadronic interactions(87%) and strange
particle decays (13%)

Eur. Phys. J. C74 (2014) 2986
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  Good agreement between
data and expectations~10%	  21	  KINEMATICAL VARIABLES
Fair agreement between data and Monte Carlo 	  Eur. Phys. J. C74 (2014) 2986µΦ	05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  D, Λc22	  THE FIRST ντ CANDIDATEAs seen by the electronic detectors …	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  Physics
LettersB691(2010) 138

23	  THE FIRST ντ CANDIDATE… and in the brick	  τ−→ρ− ντ
ρ−→π0 ππ0 → γ γ
05/01/17	  Giovanni	  De	  Lellis,	  B691
KMI	  Symposium	  Physics
Letters(2010) 138

24	  THE SECOND ντ CANDIDATEAs seen by the electronic detectors …	  05/01/17	  e	  Lellis,	  KMI	  SPhysics
ymposium	   11 (2013) 036
Journal ofGiovanni	  HighDEnergy

25	  THE SECOND ντ CANDIDATE… and in the brick	  05/01/17	  Giovanni	  De	  LEnergyellis,	  KMI	  Symposium	  Journal ofHigh
Physics 11 (2013) 036

26	  THE THIRD ντ CANDIDATEAs seen by the electronic detectors …	  2.8 GeV muon

05/01/17	  Giovanni	  De	  L(2014)ellis,	  KMI	  Symposium	  Phys. Rev.
D 89051102(R)27	  THE THIRD ντ CANDIDATE… and in the brick	  05/01/17	  Giovanni	  De	  L(2014)ellis,	  KMI	  Symposium	  Phys. Rev.
D 89051102(R)28	  THE FOURTH ντ CANDIDATEAs seen by the electronic detectors …	  05/01/17	  PTEP 10 (2014) 101C01
Giovanni	  De	  Lellis,	  KMI	  Symposium	  29	  THE FORTH ντ CANDIDATE… and in the brick	  PTEP 10 (2014) 101C01
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  30	  THE FIFTH ντ CANDIDATEAs seen by the electronic detectors …	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  31	THE FIFTH ντ CANDIDATE… and in the brick 	  PRL 115 (2015) 121802
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  32	  VISIBLE ENERGY OF ALL THE CANDIDATESSum of the momenta of charged particles and γ’s measured in emulsion05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  33	  STATISTICAL CONSIDERATIONS

Two statistical methods:- Fisher combination of single channel p-values- Profile likelihood ratio

m2 = 2.44 · 10 3 eV2

5 observed events with 0.25 background events expected{	  Fisher = 1.10 x 10-7
Probability to be explained by background
Profile likelihood = 1.07 x 10-7This corresponds to 5.1 σ significance of non-null observation

P (n 5 | µ = 2.9) = 16.6 %5 | µ = 2.9) = 16.6 %P P† (n= 6.4%
†P
† = 6.4%
P P †== probability
obtaina configuration
thanprobability to toobtaina configuration
less likelyless
thanlikely(3, 1, 1,0) (3, 1, 1, 0)
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  34	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  35	  05/01/17	  PRL 115 (2015) 121802

Giovanni	  De	  Lellis,	  KMI	  Symposium	  36	  IN THE SAME DATA SAMPLE…	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  37	  AN EVENT WITH THREE VERTICESWITHOUT ANY MUON IN THE FINAL STATE	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  38	  Track segments showing a double vertex topology
in the same lead plate

2 prong vertex
Flight Length = 103 µm	  Invariant mass = 1.9±0.5 GeV	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  39	  Leading Feynman diagrams

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  40	  Expected yield after topological selection
3Sample⌫⌧ CC + charm⌫µ CC + charm + hint⌫µ NC + cc̄
⌫⌧ CC + hint⌫µ CC + 2hint⌫µ NC + 2hint
Total

Muon misidentified
yes

yes

Expected events (10452113944100)

Multivariate Analysis

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  41	  Neutral network result and significance	  x PDF from ANN output
ni = yield of i-th process
Background only à µ = 0

CL = (2.6 ± 0.2) ⇥ 10 4 ! 3.47
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  42	  OTHER OSCILLATION ANALYSES	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  43	  STERILE NEUTRINOS	  3+1 model: bounds from ντ appearance with profile Likelihood methodm241 > 1 eV 2
After maximising over C2L̃( µ⌧ , sin2 2✓µ⌧ )1.27 m2ij L,ij =E

JHEP 1506 (2015) 069
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  44	  STERILE NEUTRINOS	  Effective mixing:	  JHEP 1506 (2015) 069

05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  45	  132
133
134
135
136

events, where 17 events were found in the procedure described in the figure2, while the other 2 events were found in the scan-back procedure mentioned
above. To illustrate the typical pattern of νe candidates, figure 5 showsµ of a eνe candidate events, with the track segments
the reconstructed image
0observed along theshowering
electrontrack.
eν →ν ANALYSIS

one of the ν events with a π as seen in the brick

JHEP 1307 (2013) 004

Interfacefilms

electronγ showers

2 mm
10 mm

ECC

CS

Figure5: Displayof the reconstructedemulsion
tracks ofνe GeV)
canAnalysis
basedon 2008-2009
run, 19 observedcandidates(4 onewithofEthe< 20didate events. The reconstructed neutrino energy is 32.5 GeV. Two tracks
interactionvertex. One of the two generates
05/01/17	   are observed at the neutrino
Giovanni	  De	  Lellis,	  KMI	  Symposium	  46	  an electromagnetic shower and is identified as an electron. In addition, twoelectromagnetic showers due to the conversion of two γ are observed (seenTable 2: Upper limits on the number of oscillated νe CC events and thesin2 (2θnew ), by F&C and Bayesian method, for C.L. 90%, 95%, 99%. The
sensitivity is computed assuming we observed 9 events, which is a most closest
integer from the expected background 9.4.

SEARCH FOR STERILE NEUTRINOS IN νµ→νe

Δ m2new (eV 2 )JHEP 1307 (2013) 004
LSND 90% C.L.

102

LSND 99% C.L.
KARMEN 90% C.L.
NOMAD 90% C.L.
BUGEY 90% C.L.

10

CHOOZ 90% C.L.
MiniBooNE 90% C.L.
MiniBooNE 99% C.L.
ICARUS 90% C.L. (F&C)

1

OPERA 90% C.L. (Bayesian)

10-1

10-2-31010-210-1

1sin2(2θnew )Figure 8: The upper limit set by this analysis using Bayesian method, together with the other limits from KARMEN(ν µ → ν e [19]), BUGEY (ν eCurrentsample extendedwith (ν~twicecandidates: 34 events
disappearance [20]), CHOOZ(ν e disappearance[21]), NOMADµ → νe[22]) and ICARUS (νµ → νe [7], using F&C method). Also shown are theregions corresponding to the positive indications reported by LSND (ν µ → ν e[5]) and MiniBooNE (νµ → νe and ν µ → ν e [6]).
1305/01/17	  New paper in preparation
Giovanni	  De	  Lellis,	  KMI	  Symposium	  47	  ONGOING EVENT ANALYSIS	  • Widen selection cuts to increase the statistics• Topological identification and looser kinematicalcuts• Statistical gain à reduce uncertainty (e.g. Δm2 fromtau appearance)• Use likelihood approach• Exploit unique feature of identifying all threeflavours: use tau appearance, electron appearance
and muon disappearance at the same time
05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  48	  05/01/17	  Giovanni	  De	  Lellis,	  KMI	  Symposium	  49