Measurement of the time-dependent CP asymmetries in B0s → J/ψK0S

JHEP06(2015)131
Published o SISSA by Sp inge
Recei ed:Ma ch 25, 2015
Accep ed:May 27, 2015
Published:June 18, 2015
Measu emen o he ime-dependen CP
asymme ies in B0
s→J/ψK0
S
The LHCb collabo a ion
E-mail: [email p o ec ed]
Abs ac : The i s measu emen o decay- ime-dependen
CP
asymme ies in he
decay
B0
s→J/ψK0
S
and an upda ed measu emen o he a io o b anching ac ions
B
(
B0
s→J/ψK0
S
)
/B
(
B0→J/ψK0
S
) a e p esen ed. The esul s a e ob ained using da a
co esponding o an in eg a ed luminosi y o 3.0 b
−1
o p o on-p o on collisions eco ded
wi h he LHCb de ec o a cen e-o -mass ene gies o 7 and 8 TeV. The esul s on he
CP
asymme ies a e
A∆Γ(B0
s→J/ψK0
S) = 0.49 ±0.77
0.65 (s a ) ±0.06(sys ) ,
Cdi (B0
s→J/ψK0
S) = −0.28 ±0.41(s a ) ±0.08(sys ) ,
Smix(B0
s→J/ψK0
S) = −0.08 ±0.40(s a ) ±0.08(sys ) .
The a io B(B0
s→J/ψK0
S)/B(B0→J/ψK0
S) is measu ed o be
0.0431 ±0.0017(s a ) ±0.0012(sys ) ±0.0025( s/ d),
whe e he las unce ain y is due o he knowledge o he
B0
s
and
B0
p oduc ion ac ions.
Keywo ds: CP iola ion, Had on-Had on Sca e ing, B anching ac ion, B physics, Fla o
physics
A Xi eP in : 1503.07055
Open Access, Copy igh CERN,
o he bene i o he LHCb Collabo a ion.
A icle unded by SCOAP3.
doi:10.1007/JHEP06(2015)131
JHEP06(2015)131
Con en s
1 In oduc ion 1
2 De ec o and simula ion 4
3 E en selec ion 4
3.1 Ini ial selec ion 4
3.2 Mul i a ia e selec ion 5
4 Fla ou agging 6
5 Likelihood i 8
5.1 Mass PDF 8
5.2 Decay ime PDF 8
5.3 Likelihood i 9
5.4 Fi esul s 10
6 Sys ema ic unce ain ies 11
7 B anching a io measu emen 12
8 Conclusion 13
The LHCb collabo a ion 17
1 In oduc ion
In decays o neu al
B
mesons (whe e
B
s ands o a
B0
o
B0
s
meson) o a inal s a e
accessible o bo h
B
and
B
, he in e e ence be ween he di ec decay and he decay ia
oscilla ion leads o decay- ime-dependen
CP
iola ion. Measu emen s o ime-dependen
CP
asymme ies p o ide aluable es s o he la ou sec o o he S anda d Model (SM) and
o e oppo uni ies o sea ch o signs o non-SM physics. A measu emen o his asymme y
in he
B0→J/ψK0
S
decay mode allows o a de e mina ion o he e ec i e
CP
phase [
1
–
3
]
φe
d(B0→J/ψK0
S)≡φd+ ∆φd,(1.1)
whe e
φd
is he ela i e phase o he
B0
–
B0
mixing ampli ude and he ee-le el decay
p ocess, and ∆
φd
is a shi induced by he so-called penguin opologies, which a e illus a ed
in igu e 1. In he S anda d Model,
φd
is equal o 2
β
[
4
], whe e
β≡a g
(
−VcdV∗
cb/V dV∗
b
)
is one o he angles o he uni a i y iangle in he Cabibbo-Kobayashi-Maskawa (CKM)
qua k mixing ma ix [
5
,
6
]. The la es a e age o he Belle and BaBa measu emen s
– 1 –
JHEP06(2015)131
eads
sin φe
d
= 0
.
665
±
0
.
020 [
7
], while he ecen ly upda ed analysis om LHCb epo s
sin φe
d= 0.729 ±0.035(s a ) ±0.022(sys ) [8].
Fo hcoming da a om he LHC and KEK
e+e−
supe
B
ac o y will lead o an unp ece-
den ed p ecision on he phase
φe
d
. To ansla e his in o an equally p ecise de e mina ion
o he CKM phase
β
, i is essen ial o ake in o accoun he doubly Cabibbo-supp essed
con ibu ions om he penguin opologies, which lead o a alue o ∆
φd
ha migh be
as la ge as
O
(1
◦
) [
1
,
3
]. By elying on app oxima e la ou symme ies, in o ma ion on
∆
φd
can be ob ained om measu emen s o
CP
asymme ies in decays whe e he penguin
opologies a e enhanced. The
B0
s→J/ψK0
S
mode is he mos p omising candida e o his
ask [2,3,9].
Assuming no
CP
iola ion in mixing [
7
], he ime-dependen
CP
asymme y in
B0
s→J/ψK0
S akes he o m
aCP ( )≡Γ(B0
s( )→J/ψK0
S)−Γ(B0
s( )→J/ψK0
S)
Γ(B0
s( )→J/ψK0
S) + Γ(B0
s( )→J/ψK0
S),(1.2)
=Smix sin (∆ms )−Cdi cos (∆ms )
cosh (∆Γs /2) + A∆Γ sinh (∆Γs /2) ,(1.3)
whe e Γ(
B0
s
(
)
→J/ψK0
S
) ep esen s he ime-dependen decay a e o he
B0
s
meson in o
he
J/ψK0
S
inal s a e, and
∆ms≡mH−mL
and
∆Γs≡ΓL−ΓH
a e, espec i ely, he
mass and decay wid h di e ence be ween he hea y and ligh eigens a es o he
B0
s
meson
sys em. The B0
s→J/ψK0
SCP obse ables a e de ined h ough he pa ame e
λJ/ψ K0
S≡ −eiφsA(B0
s→J/ψK0
S)
A(B0
s→J/ψK0
S)(1.4)
in e ms o he complex phase
φs
associa ed wi h he
B0
s
–
B0
s
mixing p ocess and he a io
o ime-independen ansi ion ampli udes as
A∆Γ ≡ −2Re[λJ/ψ K0
S]
1 + |λJ/ψ K0
S|2, Cdi ≡1−|λJ/ψ K0
S|2
1 + |λJ/ψ K0
S|2, Smix ≡2Im[λJ/ψ K0
S]
1 + |λJ/ψ K0
S|2,(1.5)
whe e
Cdi
and
Smix
ep esen di ec and mixing-induced
CP
iola ion, espec i ely. In he
S anda d Model φSM
s≡2 a g(−V sV∗
b). A ecen analysis [3] p edic s
A∆Γ B0
s→J/ψK0
S= 0.957 ±0.061 ,
Cdi B0
s→J/ψK0
S= 0.003 ±0.021 ,(1.6)
Smix B0
s→J/ψK0
S= 0.29 ±0.20 .
Simila exp ession o eqs.
(1.3)
and
(1.5)
a e ob ained o he
B0→J/ψK0
S
decay by
eplacing
s↔d
. The obse able
A∆Γ
is no applicable in he measu emen o
B0→J/ψK0
S
because i is assumed ha ∆Γd= 0 [7].
This pape p esen s he i s measu emen o he ime-dependen
CP
asymme ies in
B0
s→J/ψK0
S
decays, as well as an upda ed measu emen o he a io o ime-in eg a ed
b anching ac ions
B(B0
s→J/ψK0
S)/B(B0→J/ψK0
S)
. This a io was i s measu ed by
– 2 –
JHEP06(2015)131
B0
(s)
J/ψ
K0
S
W
b
d(s)
d(s)
c
c
s(d)
B0
(s)
J/ψ
K0
S
W
b
d(s)d(s)
s(d)
c
c
u, c,
Colou single
exchange
Figu e 1
. Decay opologies con ibu ing o he
B0
(s)→J/ψK0
S
channel: (le ) ee diag am and
( igh ) penguin diag am.
he CDF collabo a ion [
10
], while he p e iously mos p ecise measu emen was epo ed
by LHCb in e . [
11
]. The analysis is pe o med wi h a da a sample co esponding o an
in eg a ed luminosi y o 3
.
0
b−1
o p o on-p o on (
pp
) collisions, eco ded by he LHCb
expe imen a cen e-o -mass ene gies o 7 TeV and 8 TeV in 2011 and 2012, espec i ely.
The analysis p oceeds in wo s eps. The i s s ep, desc ibed in de ail in sec ion 3,
consis s o a mul i a ia e selec ion o
B→J/ψK0
S
candida es. In he second s ep a
maximum likelihood i is pe o med o he selec ed da a. The i model includes a p ominen
B0→J/ψK0
S
componen , which is used o imp o e he modelling o he
B0
s→J/ψK0
S
signal.
In addi ion, he measu emen o
CP
asymme ies associa ed wi h
B0→J/ψK0
S
decays
o e s a alida ion o he likelihood me hod’s implemen a ion. Howe e , he s ingen e en
selec ion necessa y o isola e he
B0
s→J/ψK0
S
candida es limi s he p ecision on hese
wo
CP
obse ables. Dedica ed and mo e p ecise measu emen s o he
B0→J/ψK0
SCP
obse ables a e he e o e he subjec o a sepa a e publica ion [8].
Fo a ime-dependen measu emen o
CP
iola ion i is essen ial o de e mine he ini ial
la ou o he
B
candida e, i.e. whe he i con ained a
b
o a
b
qua k a p oduc ion. The
me hod o achie e his is called la ou agging, and is discussed in sec ion 4. The agging
in o ma ion is combined wi h a desc ip ion o he
B
mass and decay ime dis ibu ions
when pe o ming he maximum likelihood i , which is desc ibed in sec ion 5. The h ee
CP
obse ables desc ibing he
B0
s→J/ψK0
S
decays and wo
CP
obse ables desc ibing he
B0→J/ψK0
S
decays a e ob ained di ec ly om he i . The a io o b anching ac ions [
12
]
is de i ed om he a io Ro i ed B0
s→J/ψK0
S o B0→J/ψK0
Se en yields as
B(B0
s→J/ψK0
S)
B(B0→J/ψK0
S)=R× sel × d
s
,(1.7)
whe e
sel
is a co ec ion ac o o di e ences in selec ion e iciency be ween
B0→J/ψK0
S
and
B0
s→J/ψK0
S
decays, and
s/ d
= 0
.
259
±
0
.
015 [
13
,
14
] is he a io o
B0
s
o
B0
meson had onisa ion ac ions. The s udy o sys ema ic e ec s on he a io
R
and he
CP
obse ables is p esen ed in sec ion 6. The main esul s o he b anching a io measu emen
a e epo ed in sec ion 7and hose o he CP obse ables in sec ion 8.
– 3 –
JHEP06(2015)131
2 De ec o and simula ion
The
LHCb
de ec o [
15
,
16
] is a single-a m o wa d spec ome e co e ing he pseudo apidi y
ange 2
< η <
5, designed o he s udy o pa icles con aining
b
o
c
qua ks. The
de ec o includes a high-p ecision acking sys em consis ing o a silicon-s ip e ex de ec o
su ounding he
pp
in e ac ion egion, a la ge-a ea silicon-s ip de ec o loca ed ups eam
o a dipole magne wi h a bending powe o abou 4
Tm
, and h ee s a ions o silicon-s ip
de ec o s and s aw d i ubes placed downs eam o he magne . The acking sys em
p o ides a measu emen o momen um,
p
, o cha ged pa icles wi h a ela i e unce ain y
ha a ies om 0.5% a low momen um o 1.0% a 200
GeV/c
. The minimum dis ance o a
ack o a p ima y e ex, he impac pa ame e , is measu ed wi h a esolu ion o (15 +
29
/pT
)
µm
, whe e
pT
is he componen o he momen um ans e se o he beam, in
GeV/c
.
Di e en ypes o cha ged had ons a e dis inguished using in o ma ion om wo ing-imaging
Che enko de ec o s. Pho ons, elec ons and had ons a e iden i ied by a calo ime e sys em
consis ing o scin illa ing-pad and p eshowe de ec o s, an elec omagne ic calo ime e and
a had onic calo ime e . Muons a e iden i ied by a sys em composed o al e na ing laye s o
i on and mul iwi e p opo ional chambe s.
In he simula ion,
pp
collisions a e gene a ed using
Py hia
[
17
,
18
] wi h a speci ic
LHCb
con igu a ion [
19
]. Decays o had onic pa icles a e desc ibed by
E Gen
[
20
],
in which inal-s a e adia ion is gene a ed using
Pho os
[
21
]. The in e ac ion o he
gene a ed pa icles wi h he de ec o , and i s esponse, a e implemen ed using he
Gean 4
oolki [22,23] as desc ibed in e . [24].
3 E en selec ion
Candida e
B→J/ψK0
S
decays a e conside ed in he
J/ψ →µ+µ−
and
K0
S→π+π−
inal s a es. The e en selec ion is based on an ini ial selec ion, ollowed by a wo-s age
mul i a ia e analysis consis ing o a i icial neu al ne wo k (NN) classi ie s [25].
3.1 Ini ial selec ion
The online e en selec ion is pe o med by a igge , which consis s o a ha dwa e le el,
based on in o ma ion om he calo ime e and muon sys ems, ollowed by a so wa e le el,
which applies a ull e en econs uc ion. The ha dwa e igge selec s a leas one muon
wi h a ans e se momen um
pT>
1
.
48 (1
.
76)
GeV/c
o wo muons wi h
ppT(µ1)pT(µ2)>
1
.
3 (1
.
6)
GeV/c
in he 7 (8)
TeV pp
collisions. The so wa e igge consis s o wo s ages.
In he i s s age, e en s a e equi ed o ha e ei he wo opposi ely cha ged muons wi h
combined mass abo e 2
.
7
GeV/c2
, o a leas one muon o one high-
pT
cha ged pa icle
(
pT>
1
.
8
GeV/c
) wi h an impac pa ame e la ge han 100
µm
wi h espec o all
pp
in e ac ion e ices (PVs). In he second s age o he so wa e igge he acks o wo o
mo e o he inal-s a e pa icles a e equi ed o o m a e ex ha is signi ican ly displaced
om he PVs, and only e en s con aining J/ψ →µ+µ−candida es a e e ained.
In he o line selec ion,
J/ψ
candida es a e selec ed by equi ing wo muon acks o
o m a good quali y e ex and ha e an in a ian mass in he ange [3030
,
3150]
MeV/c2
.
– 4 –

JHEP06(2015)131
This in e al co esponds o abou eigh imes he µ+µ−mass esolu ion a he J/ψ mass
and co e s pa o he J/ψ adia i e ail.
Decays o
K0
S→π+π−
a e econs uc ed in wo di e en ca ego ies: he i s in ol ing
K0
S
mesons ha decay ea ly enough o he daugh e pions o be econs uc ed in he e ex
de ec o ; and he second con aining
K0
S
ha decay la e such ha ack segmen s o he
pions canno be o med in he e ex de ec o . These ca ego ies a e e e ed o as long and
downs eam, espec i ely. Long
K0
S
candida es ha e be e mass, momen um and e ex
esolu ion han hose in he downs eam ca ego y.
The wo pion acks o he long (downs eam)
K0
S
candida es a e equi ed o o m a good
quali y e ex and hei combined in a ian mass mus be wi hin 35(64)
MeV/c2
o he known
K0
S
mass [
26
]. To emo e con amina ion om Λ
→pπ−
decays, he econs uc ed mass o he
long (downs eam)
K0
S
candida es unde he assump ion ha one o i s daugh e acks is a
p o on is equi ed o be mo e han 6(10)
MeV/c2
away om he known Λ mass [
26
]. The
K0
S
decay e ex is equi ed o be loca ed downs eam o he
J/ψ
decay e ex, i.e. i is equi ed
o ha e a posi i e ligh dis ance. This emo es app oxima ely 50% o mis- econs uc ed
B0→J/ψK∗(892)0
backg ound. The emaining
B0→J/ψK∗(892)0
backg ound is hea ily
supp essed by he i s s age o he mul i a ia e selec ion desc ibed below.
Candida e
B
mesons a e selec ed om combina ions o
J/ψ
and
K0
S
candida es wi h
mass
mJ/ψ K0
S
in he ange [5180
,
5520]
MeV/c2
and a decay ime la ge han 0
.
2
ps
. The
econs uc ed mass and decay ime a e ob ained om a kinema ic i [
27
] ha cons ains
he masses o he
µ+µ−
and
π+π−
pai s o he known
J/ψ
and
K0
S
masses [
26
], espec i ely,
and cons ains he
B
candida e o o igina e om he PV. A good quali y i is equi ed and
he unce ain y on he
B
mass es ima ed by he kinema ic i mus no exceed 30
MeV/c2
.
In he case ha he e en has mul iple PVs, a clea sepa a ion o he
J/ψ
decay e ex
om any o he o he PVs in he e en is equi ed, and all combina ions o
B
candida es
and PVs ha pass he selec ion a e conside ed.
3.2 Mul i a ia e selec ion
The i s s age o he mul i a ia e selec ion ocuses on emo ing he mis- econs uc ed
B0→J/ψK∗(892)0
backg ound ha su i es he equi emen on he
K0
S
ligh dis ance.
I only a ec s he subsample o candida es o which he
K0
S
is econs uc ed in he long
ca ego y. The NN is ained on simula ed
B0→J/ψK0
S
(signal) and
B0→J/ψK∗(892)0
(backg ound) da a and only uses in o ma ion associa ed wi h he econs uc ed pions and
K0
S
candida e. This includes decay ime, mass, momen um, impac pa ame e and pa icle-
iden i ica ion p ope ies. The equi emen on he NN classi ie ’s ou pu is op imised o
e ain 99% o he o iginal signal candida es in simula ion, wi h a backg ound ejec ion on
simula ed
B0→J/ψK∗(892)0
candida es o 99.55%. This esul s in an es ima ed numbe o
18
±
2
B0→J/ψK∗(892)0
candida es in he long
K0
S
da a sample su i ing his s age o he
selec ion. Thei yield is u he educed by he second NN classi ie , and hese candida es
a e he e o e ea ed as combina o ial backg ound in he emainde o he analysis.
The second s age o he mul i a ia e selec ion aims a educing he combina o ial
backg ound o isola e he small
B0
s→J/ψK0
S
signal. In con as o he i s NN, i is ained
en i ely on da a, using he
B0→J/ψK0
S
signal as a ep esen a i e o he signal ea u es o
– 5 –
JHEP06(2015)131
he
B0
s→J/ψK0
S
decay. Candida es o he aining sample a e hose popula ing he mass
anges [5180
,
5340]
MeV/c2
and [5390
,
5520]
MeV/c2
, a oiding he
B0
s
signal egion. The
signal and backg ound weigh s o he aining o he second NN a e de e mined using he
sPlo
echnique [
28
] and ob ained by pe o ming an unbinned maximum likelihood i o
he
B
mass dis ibu ion o he candida es mee ing he selec ion c i e ia on he i s NN
classi ie ’s ou pu . The i unc ion is de ined as he sum o a
B0
signal componen and a
combina o ial backg ound whe e he pa ame isa ion o he indi idual componen s ma ches
ha o he likelihood me hod used o he ull
CP
analysis and is desc ibed in mo e de ail
in sec ion 5.
Due o di e ences in he dis ibu ions o he inpu a iables o he NN, as well as
di e en signal- o-backg ound a ios, he second s age o he mul i a ia e selec ion is
pe o med sepa a ely o he
B
candida e samples con aining long and downs eam
K0
S
candida es. The NN classi ie s use in o ma ion on he candida e’s kinema ic p ope ies,
e ex and ack quali y, impac pa ame e , pa icle iden i ica ion in o ma ion om he
RICH and muon de ec o s, as well as global e en p ope ies like ack and PV mul iplici ies.
The a iables ha a e used in he second NN a e chosen o a oid co ela ions wi h he
econs uc ed Bmass.
Final selec ion equi emen s on he second s age NN classi ie ou pu s a e chosen o
op imise he sensi i i y o he
B0
s
signal using
NS/√NS+NB
as igu e o me i , whe e
NS
and
NB
a e espec i ely he expec ed numbe o signal and backg ound e en s in a
±
30
MeV/c2
mass ange a ound he
B0
s
peak. A e applying he inal equi emen on he NN
classi ie ou pu associa ed wi h he long (downs eam)
K0
S
sample, he mul i a ia e selec ion
ejec s, ela i e o he ini ial selec ion, 99.2% o he backg ound in bo h samples while
keeping 72.9% (58.3%) o he
B0
signal. The lowe selec ion e iciency on he downs eam
K0
S
sample is due o he wo se signal- o-backg ound a io a e he ini ial selec ion, which
equi es a mo e s ingen equi emen on he NN classi ie ou pu . The esul ing
J/ψK0
S
mass dis ibu ions a e illus a ed in igu e 2.
A e applying he ull selec ion, he long (downs eam)
B
candida e can s ill be
associa ed wi h mo e han one PV in abou 1.5% (0.6%) o he e en s; in his case, one PVs
is chosen a andom. Likewise, abou 0
.
24% (0.15%) o he selec ed e en s ha e mul iple
candida es sha ing one o mo e acks; in his case, one candida es is chosen a andom.
4 Fla ou agging
A he LHC,
b
qua ks a e p edominan ly p oduced in
b¯
b
pai s. When one o he wo qua ks
had onises o o m he
B
meson decay o in e es (“ he signal
B
”), he o he
b
qua k
had onises and decays independen ly. By exploi ing his p oduc ion mechanism, he signal
B
’s ini ial la ou is iden i ied by means o wo classes o la ou - agging algo i hms. The
opposi e side (OS) agge s de e mine he la ou o he non-signal
b
-had on [
29
] while he
same side kaon (SSK) agge exploi s he ac ha he addi ional
s
(
s
) qua k p oduced in
he agmen a ion o a B0
s(B0
s) meson o en o ms a K+(K−) meson [30].
These algo i hms p o ide ag decisions
qOS
and
qSSK
, which ake he alue +1 (
−
1) in
case he signal candida e is agged as a
B
(
B
) meson, and p edic ions
ηOS
and
ηSSK
o he
– 6 –
JHEP06(2015)131
)
2
cE en s / ( 2 MeV/
1
10
2
10
3
10
0
S
KLong
LHCb
)
2
c (MeV/
0
S
K
ψ
J/
m
5200 5300 5400 5500
Pull
-5
0
5
)
2
cE en s / ( 2 MeV/
1
10
2
10
3
10
4
10 0
S
KDowns eam
LHCb
)
2
c (MeV/
0
S
K
ψ
J/
m
5200 5300 5400 5500
Pull
-5
0
5
Figu e 2
. Mass dis ibu ion o
B
candida es a di e en s ages o he e en selec ion o he (le )
long
K0
S
and ( igh ) downs eam
K0
S
sample. The da a sample a e ini ial selec ion ( ed, +), a e
he i s neu al ne (g een,
×
) and a e he second neu al ne (black,
•
) a e shown. O e laid
a e p ojec ions o he i desc ibed in sec ion 5. Shown componen s a e
B0
s→J/ψK0
S
(da k blue,
dashed), B0→J/ψK0
S( ed, do ed) and combina o ial backg ound ( u quoise, dash-do ed).
p obabili y o he ag o be inco ec . The la e is ob ained using neu al ne wo ks, which
in he case o he OS agge s a e ained on
B+→J/ψK+
decays, while o he SSK agge
simula ed B0
s→D−
sπ+e en s a e used.
The mis ag p obabili y p edic ed by he agging algo i hms is calib a ed in da a o
de e mine he ue mis ag p obabili y
ω
, by using con ol samples o se e al la ou -speci ic
B
mesons decays. This calib a ion is pe o med indi idually o he OS and SSK agging
algo i hms; o he la e , di e en calib a ion pa ame e s a e used o desc ibe he
B0
and
B0
s
mesons. Fo all e en s wi h bo h an OS and SSK ag decision, a combined ag decision
and mis ag p obabili y is de i ed as desc ibed in e . [29].
The igu e o me i o he op imisa ion o a agging algo i hm is he e ec i e agging
e iciency,
εe
=
ε ag
(1
−
2
ω
)
2
whe e
ε ag
is he ac ion o candida es wi h an assigned ag
decision. In he long
K0
S
sample o he
B0
s→J/ψK0
S
mode, he OS and SSK agge s yield
an
εe
o (2
.
93
±
0
.
06)% and (0
.
97
±
0
.
12)%, espec i ely, while he sample wi h bo h an
OS and SSK agging esponse gi es an
εe
o (1
.
02
±
0
.
10)%. In he espec i e downs eam
K0
S
sample, he OS and SSK agge s yield an
εe
o (2
.
74
±
0
.
11)% and (1
.
45
±
0
.
15)%,
espec i ely, while he sample wi h bo h an OS and SSK agging esponse gi es an
εe
o
(0
.
48
±
0
.
04)%. The combined
εe
o all h ee o e lapping samples o he
B0
s→J/ψK0
S
mode is measu ed o be (3
.
80
±
0
.
18)% and (4
.
03
±
0
.
16)% in he long and downs eam
K0
S
sample, espec i ely.
In he
B0→J/ψK0
S
mode, he main con ibu ion is p o ided by he OS agge s,
whe e he combined
εe
is measu ed o be (2
.
60
±
0
.
05)% and (2
.
63
±
0
.
05)% in he
long and downs eam
K0
S
sample, espec i ely. Al hough he SSK agging algo i hm is
– 7 –
JHEP06(2015)131
Pa ame e Value Pa ame e Value
∆md0.510 ±0.003 ps−1[7] ∆ms17.757 ±0.021 ps−1[7]
∆Γd0 ps−1∆Γs0.081 ±0.006 ps−1[7]
τBd1.520 ±0.004 ps [7]τBs1.509 ±0.004 ps [7]
Table 1
. Lis o he obse ables desc ibing he
B0
and
B0
s
sys ems ha a e included as Gaussian
cons ain s o he likelihood i .
speci ically designed o
B0
s
mesons, a small, bu non- anishing e ec i e agging e iciency o
(0
.
064
±
0
.
009)% and (0
.
098
±
0
.
013)% in he long and downs eam
K0
S
sample, espec i ely,
is also ound o
B0
mesons i he ag decision is e e sed. This e ec o igina es om
same-side p o ons mis-iden i ied as kaons, and kaons om he decay o
K∗
(892)
0
mesons
p oduced in co ela ion wi h he
B0
. Bo h agged pa icles ha e a cha ge opposi e o hose
o kaons p oduced in co ela ion wi h he
B0
s
, and hus equi e he SSK ag decision o be
in e ed. Addi ionally, mis-iden i ied pions ca ying he same cha ge as he kaons co ela ed
wi h he
B0
s
dilu e he e ec desc ibed abo e. The SSK agging esponse o
B0
candida es
is s udied on B0→J/ψ K∗(892)0candida es using bo h da a and simula ed e en s.
5 Likelihood i
The
B0
s→J/ψK0
SCP
obse ables a e de e mined om an unbinned maximum likelihood
i . The da a is i ed wi h a p obabili y densi y unc ion (PDF) de ined as he sum
o a
B0
signal componen , a
B0
s
signal componen and a combina o ial backg ound. In
o al i depends on se en obse ables. The PDF desc ibes he econs uc ed
B
mass
(
mJ/ψ K0
S∈
[5180
,
5520]
MeV/c2
), he decay ime (
∈
[0
.
2
,
15]
ps
), and agging esponses
qOS
and
qSSK
. Addi ionally, i also depends on he pe -candida e decay ime unce ain y
es ima e
δ
and mis ag es ima es
ηOS
and
ηSSK
. The long and downs eam
K0
S
samples
a e modelled using sepa a e PDFs bu i ed simul aneously. The pa ame e s common o
bo h PDFs a e he wo
B0→J/ψK0
S
and h ee
B0
s→J/ψK0
SCP
obse ables, as well as
he obse ables desc ibing he B0and B0
ssys ems ha a e lis ed in able 1.
5.1 Mass PDF
The mass shapes o he
B→J/ψK0
S
modes in bo h da a and simula ion exhibi non-
Gaussian ails on bo h sides o hei signal peaks due o inal-s a e adia ion, he de ec o
esolu ion and i s dependence on he momen a o he inal-s a e pa icles. Each signal shape
is pa ame ised by a Hypa ia unc ion [
31
], whose ail pa ame e s a e aken om simula ion.
The
B0
s
componen is cons ained o ha e he same shape as he
B0
PDF, bu shi ed by
he
B0
s
–
B0
mass di e ence, which is a ee a iable in he i . The mass dis ibu ion o he
combina o ial backg ound is desc ibed by an exponen ial unc ion.
5.2 Decay ime PDF
The decay ime dis ibu ions o he wo signal componen s,
T
(
, qOS, qSSK|ηOS, ηSSK
), need
o be co ec ed o expe imen al e ec s o igina ing om he de ec o esponse and he e en
– 8 –
JHEP06(2015)131
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JHEP06(2015)131
The LHCb collabo a ion
R. Aaij41, B. Ade a37, M. Adinol i46, A. A olde 52, Z. Ajal ouni5, S. Aka 6, J. Alb ech 9,
F. Alessio38, M. Alexande 51, S. Ali41, G. Alkhazo 30, P. Al a ez Ca elle53, A.A. Al es J 57,
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J.E. And ews58, R.B. Appleby54, O. Aquines Gu ie ez10, F. A chilli38, A. A amono 35,
M. A uso59, E. Aslanides6, G. Au iemma25,n, M. Baalouch5, S. Bachmann11, J.J. Back48,
A. Badalo
36
, C. Baesso
60
, W. Baldini
16,38
, R.J. Ba low
54
, C. Ba schel
38
, S. Ba suk
7
, W. Ba e
38
,
V. Ba ozskaya28, V. Ba is a39, A. Bay39, L. Beaucou 4, J. Beddow51, F. Bedeschi23, I. Bediaga1,
L.J. Bel
41
, I. Belyae
31
, E. Ben-Haim
8
, G. Benci enni
18
, S. Benson
38
, J. Ben on
46
, A. Be ezhnoy
32
,
R. Be ne
40
, A. Be olin
22
, M.-O. Be le
38
, M. an Beuzekom
41
, A. Bien
11
, S. Bi ani
45
, T. Bi d
54
,
A. Bizze i17,i, T. Blake48, F. Blanc39, J. Blouw10, S. Blusk59, V. Bocci25, A. Bonda 34,
N. Bonda 30,38, W. Boni en o15, S. Bo ghi54, A. Bo gia59, M. Bo sa o7, T.J.V. Bowcock52,
E. Bowen40, C. Bozzi16, S. B aun11, D. B e 54, M. B i sch10, T. B i on59, J. B odzicka54,
N.H. B ook46, A. Bu sche40, J. Buy ae 38, S. Cadeddu15, R. Calab ese16, , M. Cal i20,k,
M. Cal o Gomez36,p, P. Campana18, D. Campo a Pe ez38, L. Cap io i54, A. Ca bone14,d,
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S.-F. Cheung
55
, N. Chiapolini
40
, M. Ch zaszcz
40,26
, X. Cid Vidal
38
, G. Cieza ek
41
, P.E.L. Cla ke
50
,
M. Clemencic38, H.V. Cli 47, J. Closie 38, V. Coco38, J. Cogan6, E. Cogne as5, V. Cogoni15,e,
L. Cojoca iu29, G. Collazuol22, P. Collins38, A. Come ma-Mon ells11, A. Con u15,38, A. Cook46,
M. Coombes46, S. Coque eau8, G. Co i38, M. Co o16, , I. Coun s56, B. Cou u ie 38,
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F. De o i38, B. Dey40, A. Di Can o38, F. Di Ruscio24, H. Dijks a38, S. Donlea y52, F. Do dei11,
M. Do igo39, A. Dosil Su´a ez37, D. Dosse 48, A. Do bnya43, K. D eimanis52, G. Dujany54,
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U. Egede53, V. Ego yche 31, S. Eidelman34, S. Eisenha d 50, U. Ei schbe ge 9, R. Ekelho 9,
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E. Fu a o
24,l
, A. Gallas To ei a
37
, D. Galli
14,d
, S. Gallo ini
22,38
, S. Gambe a
19,j
, M. Gandelman
2
,
P. Gandini55, Y. Gao3, J. Ga c´ıa Pa di˜nas37, J. Ga o oli59, J. Ga a Tico47, L. Ga ido36,
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E. Ge sabeck
11
, M. Ge sabeck
54
, T. Ge shon
48
, Ph. Ghez
4
, A. Gianelle
22
, S. Gian`ı
39
, V. Gibson
47
,
L. Giubega29, V.V. Gligo o 38, C. G¨obel60, D. Golubko 31, A. Golu in53,31,38, A. Gomes1,a,
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O. G ¨unbe g
63
, E. Gushchin
33
, Yu. Guz
35,38
, T. Gys
38
, C. Hadji asiliou
59
, G. Hae eli
39
, C. Haen
38
,
S.C. Haines47, S. Hall53, B. Hamil on58, T. Hampson46, X. Han11, S. Hansmann-Menzeme 11,
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– 17 –
JHEP06(2015)131
D. Hu chc o 52, D. Hynds51, M. Idzik27, P. Il en56, R. Jacobsson38, A. Jaege 11, J. Jalocha55,
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41
, A. Jawahe y
58
, F. Jing
3
, M. John
55
, D. Johnson
38
, C.R. Jones
47
, C. Jo am
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, B. Jos
38
,
N. Ju ik
59
, S. Kandybei
43
, W. Kanso
6
, M. Ka acson
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, T.M. Ka bach
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, S. Ka odia
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, M. Kelsey
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,
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42
, G. Lan anchi
18
, C. Langenb uch
48
, B. Langhans
38
, T. La ham
48
, C. Lazze oni
45
,
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T. Lesiak26, B. Le e ing on11, Y. Li7, T. Likhomanenko64, M. Liles52, R. Lindne 38, C. Linn38,
F. Lione o40, B. Liu15, S. Lohn38, I. Longs a 51, J.H. Lopes2, P. Lowdon40, D. Lucchesi22, ,
H. Luo50, A. Lupa o22, E. Luppi16, , O. Lup on55, F. Mache e 7, I.V. Machikhiliyan31,
F. Maciuc29, O. Mae 30, S. Malde55, A. Malinin64, G. Manca15,e, G. Mancinelli6, P. Manning59,
A. Mapelli38, J. Ma a as5, J.F. Ma chand4, U. Ma coni14, C. Ma in Beni o36, P. Ma ino23,38, ,
R. M¨a ki39, J. Ma ks11, G. Ma ello i25, M. Ma inelli39, D. Ma inez San os42,
F. Ma inez Vidal
66
, D. Ma ins Tos es
2
, A. Massa e i
1
, R. Ma e
38
, Z. Ma he
38
, C. Ma euzzi
20
,
A. Mau i
40
, B. Mau in
39
, A. Mazu o
45
, M. McCann
53
, J. McCa hy
45
, A. McNab
54
, R. McNul y
12
,
B. McSkelly52, B. Meadows57, F. Meie 9, M. Meissne 11, M. Me k41, D.A. Milanes62,
M.-N. Mina d4, J. Molina Rod iguez60, S. Mon eil5, M. Mo andin22, P. Mo awski27, A. Mo d`a6,
M.J. Mo ello23, , J. Mo on27, A.-B. Mo is50, R. Moun ain59, F. Muheim50, K. M¨ulle 40,
M. Mussini
14
, B. Mus e
39
, P. Naik
46
, T. Nakada
39
, R. Nandakuma
49
, I. Nas e a
2
, M. Needham
50
,
N. Ne i21, S. Neube 11, N. Neu eld38, M. Neune 11, A.D. Nguyen39, T.D. Nguyen39,
C. Nguyen-Mau39,q, V. Niess5, R. Nie 9, N. Niki in32, T. Nikodem11, A. No oselo 35,
D.P. O’Hanlon48, A. Oblakowska-Mucha27, V. Ob az so 35, S. Ogil y51, O. Okh imenko44,
R. Oldeman15,e, C.J.G. Onde wa e 67, B. Oso io Rod igues1, J.M. O alo a Goicochea2, A. O o38,
P. Owen53, A. Oyangu en66, A. Palano13,c, F. Palombo21,u, M. Palu an18, J. Panman38,
A. Papanes is49, M. Pappagallo51, L.L. Pappala do16, , C. Pa kes54, G. Passale a17, G.D. Pa el52,
M. Pa el53, C. Pa ignani19,j, A. Pea ce54,49, A. Pelleg ino41, G. Penso25,m, M. Pepe Al a elli38,
S. Pe azzini14,d, P. Pe e 5, L. Pesca o e45, K. Pe idis46, A. Pe olini19,j, E. Pica os e Olloqui36,
B. Pie zyk4, T. Pilaˇ 48, D. Pinci25, A. Pis one19, S. Play e 50, M. Plo Casasus37, T. Poikela38,
F. Polci8, A. Poluek o 48,34, I. Polyako 31, E. Polyca po2, A. Popo 35, D. Popo 10, B. Popo ici29,
C. Po e a
2
, E. P ice
46
, J.D. P ice
52
, J. P iscianda o
39
, A. P i cha d
52
, C. P ou e
46
, V. Puga ch
44
,
A. Puig Na a o39, G. Punzi23,s, W. Qian4, R. Quagliani7,46, B. Rachwal26, J.H. Rademacke 46,
B. Rako omia amanana39, M. Rama23, M.S. Rangel2, I. Raniuk43, N. Rauschmay 38, G. Ra en42,
F. Redi53, S. Reiche 54, M.M. Reid48, A.C. dos Reis1, S. Riccia di49, S. Richa ds46, M. Rihl38,
K. Rinne 52, V. Ri es Molina36, P. Robbe7,38, A.B. Rod igues1, E. Rod igues54,
J.A. Rod iguez Lopez62, P. Rod iguez Pe ez54, S. Roise 38, V. Romano sky35, A. Rome o Vidal37,
M. Ro ondo22, J. Rou ine 39, T. Ru 38, H. Ruiz36, P. Ruiz Valls66, J.J. Sabo ido Sil a37,
N. Sagido a30, P. Sail51, B. Sai a15,e, V. Salus ino Guima aes2, C. Sanchez Mayo domo66,
B. Sanma in Sedes37, R. San acesa ia25, C. San ama ina Rios37, E. San o e i24,l, A. Sa i18,m,
C. Sa iano25,n, A. Sa a24, D.M. Saunde s46, D. Sa ina31,32, M. Schille 38, H. Schindle 38,
M. Schlupp9, M. Schmelling10, B. Schmid 38, O. Schneide 39, A. Schoppe 38, M.-H. Schune7,
R. Schwemme 38, B. Sciascia18, A. Sciubba25,m, A. Semenniko 31, I. Sepp53, N. Se a40,
J. Se ano
6
, L. Ses ini
22
, P. Sey e
11
, M. Shapkin
35
, I. Shapo al
16,43,
, Y. Shcheglo
30
, T. Shea s
52
,
L. Shekh man34, V. She chenko64, A. Shi es9, R. Sil a Cou inho48, G. Simi22, M. Si endi47,
N. Skidmo e
46
, I. Skillico n
51
, T. Skwa nicki
59
, N.A. Smi h
52
, E. Smi h
55,49
, E. Smi h
53
, J. Smi h
47
,
M. Smi h54, H. Snoek41, M.D. Sokolo 57,38, F.J.P. Sole 51, F. Soom o39, D. Souza46,
– 18 –
JHEP06(2015)131
B. Souza De Paula2, B. Spaan9, P. Sp adlin51, S. S idha an38, F. S agni38, M. S ahl11, S. S ahl38,
O. S einkamp
40
, O. S enyakin
35
, F. S e pka
59
, S. S e enson
55
, S. S oica
29
, S. S one
59
, B. S o aci
40
,
S. S acka23, , M. S a iciuc29, U. S aumann40, R. S oili22, L. Sun57, W. Su cli e53,
K. Swien ek27, S. Swien ek9, V. Sy opoulos42, M. Szczekowski28, P. Szczypka39,38, T. Szumlak27,
S. T’Jampens4, M. Teklishyn7, G. Tella ini16, , F. Teube 38, C. Thomas55, E. Thomas38,
J. an Tilbu g41, V. Tisse and4, M. Tobin39, J. Todd57, S. Tolk42, L. Tomasse i16, , D. Tonelli38,
S. Topp-Joe gensen55, N. To 55, E. Tou ne ie 4, S. Tou neu 39, K. T abelsi39, M.T. T an39,
M. T esch
40
, A. T iso ic
38
, A. Tsa ego od se
6
, P. Tsopelas
41
, N. Tuning
41,38
, M. Ubeda Ga cia
38
,
A. Ukleja28, A. Us yuzhanin65, U. Uwe 11, C. Vacca15,e, V. Vagnoni14, G. Valen i14, A. Vallie 7,
R. Vazquez Gomez18, P. Vazquez Reguei o37, C. V´azquez Sie a37, S. Vecchi16, J.J. Vel huis46,
M. Vel i17,h, G. Veneziano39, M. Ves e inen11, J.V. Viana Ba bosa38, B. Viaud7, D. Viei a2,
M. Viei es Diaz37, X. Vilasis-Ca dona36,p, A. Vollha d 40, D. Volyanskyy10, D. Voong46,
A. Vo obye 30, V. Vo obye 34, C. Voß63, J.A. de V ies41, R. Waldi63, C. Wallace48, R. Wallace12,
J. Walsh23, S. Wande no h11, J. Wang59, D.R. Wa d47, N.K. Wa son45, D. Websdale53,
A. Weiden40, M. Whi ehead48, D. Wiedne 11, G. Wilkinson55,38, M. Wilkinson59, M. Williams38,
M.P. Williams45, M. Williams56, H.W. Wilschu 67, F.F. Wilson49, J. Wimbe ley58, J. Wishahi9,
W. Wislicki28, M. Wi ek26, G. Wo mse 7, S.A. Wo on47, S. W igh 47, K. Wyllie38, Y. Xie61,
Z. Xu39, Z. Yang3, X. Yuan34, O. Yushchenko35, M. Zangoli14, M. Za e yae 10,b, L. Zhang3,
Y. Zhang3, A. Zhelezo 11, A. Zhokho 31, L. Zhong3.
1Cen o B asilei o de Pesquisas F´ısicas (CBPF), Rio de Janei o, B azil
2Uni e sidade Fede al do Rio de Janei o (UFRJ), Rio de Janei o, B azil
3Cen e o High Ene gy Physics, Tsinghua Uni e si y, Beijing, China
4LAPP, Uni e si ´e Sa oie Mon -Blanc, CNRS/IN2P3, Annecy-Le-Vieux, F ance
5Cle mon Uni e si ´e, Uni e si ´e Blaise Pascal, CNRS/IN2P3, LPC, Cle mon -Fe and, F ance
6CPPM, Aix-Ma seille Uni e si ´e, CNRS/IN2P3, Ma seille, F ance
7LAL, Uni e si ´e Pa is-Sud, CNRS/IN2P3, O say, F ance
8LPNHE, Uni e si ´e Pie e e Ma ie Cu ie, Uni e si ´e Pa is Dide o , CNRS/IN2P3, Pa is, F ance
9Fakul ¨a Physik, Technische Uni e si ¨a Do mund, Do mund, Ge many
10 Max-Planck-Ins i u ¨u Ke nphysik (MPIK), Heidelbe g, Ge many
11 Physikalisches Ins i u , Rup ech -Ka ls-Uni e si ¨a Heidelbe g, Heidelbe g, Ge many
12 School o Physics, Uni e si y College Dublin, Dublin, I eland
13 Sezione INFN di Ba i, Ba i, I aly
14 Sezione INFN di Bologna, Bologna, I aly
15 Sezione INFN di Caglia i, Caglia i, I aly
16 Sezione INFN di Fe a a, Fe a a, I aly
17 Sezione INFN di Fi enze, Fi enze, I aly
18 Labo a o i Nazionali dell’INFN di F asca i, F asca i, I aly
19 Sezione INFN di Geno a, Geno a, I aly
20 Sezione INFN di Milano Bicocca, Milano, I aly
21 Sezione INFN di Milano, Milano, I aly
22 Sezione INFN di Pado a, Pado a, I aly
23 Sezione INFN di Pisa, Pisa, I aly
24 Sezione INFN di Roma To Ve ga a, Roma, I aly
25 Sezione INFN di Roma La Sapienza, Roma, I aly
26 Hen yk Niewodniczanski Ins i u e o Nuclea Physics Polish Academy o Sciences, K ak´ow, Poland
27 AGH - Uni e si y o Science and Technology, Facul y o Physics and Applied Compu e Science,
K ak´ow, Poland
28 Na ional Cen e o Nuclea Resea ch (NCBJ), Wa saw, Poland
29
Ho ia Hulubei Na ional Ins i u e o Physics and Nuclea Enginee ing, Bucha es -Magu ele, Romania
30 Pe e sbu g Nuclea Physics Ins i u e (PNPI), Ga china, Russia
– 19 –
JHEP06(2015)131
31 Ins i u e o Theo e ical and Expe imen al Physics (ITEP), Moscow, Russia
32 Ins i u e o Nuclea Physics, Moscow S a e Uni e si y (SINP MSU), Moscow, Russia
33 Ins i u e o Nuclea Resea ch o he Russian Academy o Sciences (INR RAN), Moscow, Russia
34
Budke Ins i u e o Nuclea Physics (SB RAS) and No osibi sk S a e Uni e si y, No osibi sk, Russia
35 Ins i u e o High Ene gy Physics (IHEP), P o ino, Russia
36 Uni e si a de Ba celona, Ba celona, Spain
37 Uni e sidad de San iago de Compos ela, San iago de Compos ela, Spain
38 Eu opean O ganiza ion o Nuclea Resea ch (CERN), Gene a, Swi ze land
39 Ecole Poly echnique F´ed´e ale de Lausanne (EPFL), Lausanne, Swi ze land
40 Physik-Ins i u , Uni e si ¨a Z¨u ich, Z¨u ich, Swi ze land
41 Nikhe Na ional Ins i u e o Suba omic Physics, Ams e dam, The Ne he lands
42 Nikhe Na ional Ins i u e o Suba omic Physics and VU Uni e si y Ams e dam, Ams e dam, The
Ne he lands
43 NSC Kha ki Ins i u e o Physics and Technology (NSC KIPT), Kha ki , Uk aine
44 Ins i u e o Nuclea Resea ch o he Na ional Academy o Sciences (KINR), Kyi , Uk aine
45 Uni e si y o Bi mingham, Bi mingham, Uni ed Kingdom
46 H.H. Wills Physics Labo a o y, Uni e si y o B is ol, B is ol, Uni ed Kingdom
47 Ca endish Labo a o y, Uni e si y o Camb idge, Camb idge, Uni ed Kingdom
48 Depa men o Physics, Uni e si y o Wa wick, Co en y, Uni ed Kingdom
49 STFC Ru he o d Apple on Labo a o y, Didco , Uni ed Kingdom
50 School o Physics and As onomy, Uni e si y o Edinbu gh, Edinbu gh, Uni ed Kingdom
51 School o Physics and As onomy, Uni e si y o Glasgow, Glasgow, Uni ed Kingdom
52 Oli e Lodge Labo a o y, Uni e si y o Li e pool, Li e pool, Uni ed Kingdom
53 Impe ial College London, London, Uni ed Kingdom
54 School o Physics and As onomy, Uni e si y o Manches e , Manches e , Uni ed Kingdom
55 Depa men o Physics, Uni e si y o Ox o d, Ox o d, Uni ed Kingdom
56 Massachuse s Ins i u e o Technology, Camb idge, MA, Uni ed S a es
57 Uni e si y o Cincinna i, Cincinna i, OH, Uni ed S a es
58 Uni e si y o Ma yland, College Pa k, MD, Uni ed S a es
59 Sy acuse Uni e si y, Sy acuse, NY, Uni ed S a es
60 Pon i ´ıcia Uni e sidade Ca ´olica do Rio de Janei o (PUC-Rio), Rio de Janei o, B azil, associa ed
o 2
61
Ins i u e o Pa icle Physics, Cen al China No mal Uni e si y, Wuhan, Hubei, China, associa ed o
3
62 Depa amen o de Fisica , Uni e sidad Nacional de Colombia, Bogo a, Colombia, associa ed o 8
63 Ins i u ¨u Physik, Uni e si ¨a Ros ock, Ros ock, Ge many, associa ed o 11
64 Na ional Resea ch Cen e Ku cha o Ins i u e, Moscow, Russia, associa ed o 31
65 Yandex School o Da a Analysis, Moscow, Russia, associa ed o 31
66 Ins i u o de Fisica Co puscula (IFIC), Uni e si a de Valencia-CSIC, Valencia, Spain, associa ed
o 36
67 Van Swinde en Ins i u e, Uni e si y o G oningen, G oningen, The Ne he lands, associa ed o 41
aUni e sidade Fede al do T iˆangulo Minei o (UFTM), Ube aba-MG, B azil
bP.N. Lebede Physical Ins i u e, Russian Academy o Science (LPI RAS), Moscow, Russia
cUni e si `a di Ba i, Ba i, I aly
dUni e si `a di Bologna, Bologna, I aly
eUni e si `a di Caglia i, Caglia i, I aly
Uni e si `a di Fe a a, Fe a a, I aly
gUni e si `a di Fi enze, Fi enze, I aly
hUni e si `a di U bino, U bino, I aly
iUni e si `a di Modena e Reggio Emilia, Modena, I aly
jUni e si `a di Geno a, Geno a, I aly
kUni e si `a di Milano Bicocca, Milano, I aly
lUni e si `a di Roma To Ve ga a, Roma, I aly
– 20 –

JHEP06(2015)131
mUni e si `a di Roma La Sapienza, Roma, I aly
nUni e si `a della Basilica a, Po enza, I aly
oAGH - Uni e si y o Science and Technology, Facul y o Compu e Science, Elec onics and
Telecommunica ions, K ak´ow, Poland
pLIFAELS, La Salle, Uni e si a Ramon Llull, Ba celona, Spain
qHanoi Uni e si y o Science, Hanoi, Vie Nam
Uni e si `a di Pado a, Pado a, I aly
sUni e si `a di Pisa, Pisa, I aly
Scuola No male Supe io e, Pisa, I aly
uUni e si `a degli S udi di Milano, Milano, I aly
Poli ecnico di Milano, Milano, I aly
– 21 –