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Nuclea Ins . and Me hods in Physics Resea ch, A
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Exposing a dual- eadou ib e calo ime e o elec on beams, in p epa a ion
o HiDRa: High- esolu ion calo ime e o π+πβcollide s
And ea Pa e i 1
Uni e si Γ degli S udi di Pa ia, Via Bassi 6, 27100, Pa ia, I aly and INFN
ARTICLE INFO
Keywo ds:
Calo ime y
Silicon pho omul iplie
De ec o R&D
ABSTRACT
Among he p oposed accele a o s o he pos -LHC e a a e he Fu u e Ci cula Collide (FCC) and he Ci cula
Elec onβPosi on Collide (CEPC). Bo h p ojec s would ake ad an age o he clean en i onmen and low
adia ion damage o elec onβposi on collisions, p o iding he highes p ecision s udies o elec oweak and
Higgs physics. The ela i ely high b anching ac ion o W, Z and Higgs bosons in o had onic je s makes he
p ecise measu emen s o hese objec s an essen ial aspec on de ec o de elopmen o expe imen s a u u e
collide acili ies. One o he mos p omising calo ime y echniques o imp o ed had on ene gy econs uc ion
is he dual- eadou me hod, which exploi s signals om wo di e en physics p ocesses o co ec o he
πππ o had on showe s, he e o e boos ing he s andalone calo ime e pe o mance. The usage o compac
pho osenso s (e.g. Silicon Pho oMul iplie s) o he eadou enables a e y ine segmen a ion, opening o
pa icle- low and ad anced neu al ne wo ks so wa e econs uc ion o e en s. In his con ibu ion, he esul s
o es ing a small-scale dual- eadou calo ime e p o o ype, cha ac e ised by a mixed PMT and SiPM eadou
solu ion, wi h an elec on beam a he CERN SPS acili y in he ene gy ange [10, 120] GeV a e p esen ed. I
ollows he desc ip ion o a la ge p o o ype o he same ype, cu en ly unde cons uc ion in he con ex o
he INFN HiDRa p ojec , ha will be la ge enough o ully con ain had on showe s. The design, cons uc ion
echnique and expec ed pe o mance, as es ima ed h ough a Gean 4 simula ion pa ame e ised on he p e ious
p o o ype, a e p esen ed.
1. In oduc ion
Excellen measu emen s o had on je ene gies a e one o he open
issues o cu en ly ope a ing collide expe imen s. These objec a e
inhe en ly complica ed by he high mul iplici y o low ene gy had ons,
each concu ing wi h luc ua ions on he elec omagne ic ac ion πππ
and on he in isible ene gy, which a e he main limi ing ac o s on he
ene gy measu emen o single had ons. One o he majo challenges on
de ec o de elopmen o u u e π+πβcollide s, he FCC o CEPC, is he
capabili y o ecognise he Higgs- ela ed p ocesses also in comple ely
had onic inal s a es (mainly π+πββππ» β4π) om he π+πββ
π+πββππ β4πbackg ound. To achie e his, he W and Z bosons
a e equi ed o be s a is ically sepa a ed, based on he in a ian mass
o he wo pai s o had on je s. This iden i ica ion equi emen poses
a s ic benchma k on calo ime ic pe o mances: an ene gy esolu ion
o 4β5% o 50 GeV je s, o equi alen ly πβπΈ= 30%ββπΈ, a e usually
epo ed as a ge .
The dual- eadou me hod [1] aims o each his esolu ion by mea-
su ing signals p oduced by ac i e ma e ials wi h di e en (ββπ) e-
sponses o he elec omagne ic and non-elec omagne ic componen s o
E-mail add ess: [emailΒ p o ec ed].
1On behal o he ECFA-DRD6 Collabo a ion, dual- eadou calo ime e wo king g oup.
had on showe s, co ec ing o he πππ on e en -by-e en basis. In mos
cases, Δe enko ligh emission is used, alongside wi h a scin illa ing
ac i e ma e ial: Δe enko ligh in had on showe s is mos ly emi ed
by elec ons and posi ons, he e o e p o iding a measu emen o he
elec omagne ic componen . The ad an ages o his me hod a e ha ,
once he co ec ion o πππ has been applied, he same ene gy scale
o bo h elec omagne ic and had onic showe s can be used, and he
econs uc ed ene gy dis ibu ion is gaussian-shaped. The IDEA de ec-
o , which was included in bo h he FCC and CEPC Concep ual Design
Repo s, uses a dual- eadou calo ime e based on op ical ib es. The
ib es in such a calo ime e , pa allel o he adial di ec ion and poin ing
o he in e ac ion poin , a e no longi udinally segmen ed, and play he
ole o bo h he ac i e ma e ial and wa e guide o signals ex ac ion
om inside he calo ime e . A ew ea ly esul s om he DD4hep
simula ion o his calo ime e can be ound in [2]. A di e en de ec o
layou , consis ing o a c ys al-based dual- eadou calo ime e sec ion
o enhanced measu emen s o elec omagne ic showe s in on o he
had onic one, has also been p oposed. Fas pho osenso s wi h single
pho on de ec ion capabili ies (SiPMs) would be used o he eadou o
h ps://doi.o g/10.1016/j.nima.2024.169890
Recei ed 29 June 2024; Recei ed in e ised o m 5 Augus 2024; Accep ed 15 Sep embe 2024
Nuclea Ins umen s and Me hods in Physics Resea ch A 1069 (2024) 169890
A ailable online 18 Sep embe 2024
0168-9002/Β© 2024 The Au ho . Published by Else ie B.V. This is an open access a icle unde he CC BY license ( h p://c ea i ecommons.o g/licenses/by/4.0/ ).
A. Pa e i
Fig. 1. Side iew o he calo ime e p o o ype, and ske ch o he beam ins umen a ion
se up o he 2021 es beam, aken om [3].
each op ical ib e, allowing o a ine la e al segmen a ion use ul o
pa icle- low and neu al ne wo k applica ions. The iming in o ma ion
p o ided by SiPMs, wi h an app op ia e eadou elec onics, could be
exploi ed o ob ain in o ma ion on pho on p oduc ion dep h inside he
op ical ib es, hence pa ially eco e he longi udinal segmen a ion.
2. Elec omagne ic-showe -size p o o ype
In o de o demons a e he easibili y o single ib e eadou wi h
SiPMs associa ed o a dual- eadou calo ime e , a i s small-scale p o-
o ype able o con ain elec on-induced showe s was buil , shown in
Fig. 1. The o e all dimensions o his p o o ype a e 10 Γ10 Γ100 cm3.
B ass capilla y ubes wi h an ou e diame e o 2 mm and an inne one
o 1.1 mm a e used as abso be . The ac i e ma e ial consis s o al e na -
ing ows o scin illa ing and clea op ical ib es o collec ing Δe enko
ligh . The ib es, 1 mm diame e , a e inse ed in o he b ass ubes. The
emaining olume o he calo ime e , be ween he capilla ies, is illed
wi h he glue deposi ed du ing he p o o ype cons uc ion p ocedu e
and, e en ually, ai . A modula design was selec ed o he p o o ype
assembly, wi h each module consis ing o 20 ows o ubes and 16
ubes pe ow. The whole p o o ype consis s o 9 modules, wi h 320
ubes each. Conce ning he eadou , a mixed PMT and SiPM solu ion is
used. The cen al module, whe e he es pa icle beam is impinging,
has a single- ib e, SiPM-based (Hamama su S14160-1315PS) eadou
o in-dep h g anula i y s udies. The emaining eigh modules on he
pe ime e a e equipped wi h wo PMTs each, Hamama su R8900 o
scin illa ing and R8900-100 wi h ex ended UV ange o Δe enko
channels, espec i ely.
This p o o ype was i s ly exposed o a posi on beam a he DESY
labo a o ies (Ge many) o a i s equalisa ion and calib a ion se up. I
was hen aken wice on he H8 beamline a he CERN SPS No h A ea
o a beam es wi h posi ons a ene gies up o 120 GeV, in 2021 and
hen 2023. A ew esul s on he wo SPS es beams a e epo ed in
he ollowing, while mo e de ails on he i s H8 beamline esul s a e
p esen ed in [3].
The beam es se up included wo Δe enko coun e s o posi on se-
lec ion ou o muon and had on componen s ups eam in he beamline,
ollowed by wo Delay Wi e Chambe s (DWCs) o es ima e he impac
poin posi ion on he calo ime e on ace. A p e-showe de ec o
was also used o complemen a y pa icle iden i ica ion pu poses. Th ee
scin illa o pla es loca ed be o e he calo ime e we e used o he ig-
ge ing. A ou h scin illa o pla e was also placed a e he calo ime e
o muon iden i ica ion. A ew p oblems we e encoun e ed du ing his
i s beam es : due o access limi a ions in he expe imen al a ea, he
p e-showe de ec o could only be placed e y a om he calo ime e ,
a ew me es ups eam he beamline, causing non-op imal con ainmen
o elec omagne ic showe s inside he limi ed p o o ype olume. The
calo ime e was also only il ed 1β¦on he ho izon al di ec ion wi h
espec o he beamline axis. The small il ing angle esul ed in a
Fig. 2. La e al p o ile o posi on-o igina ed showe s, measu ed h ough he highly
g anula co e o he calo ime e p o o ype. I shows he ac ion o ene gy deposi ed
inside a adius π om he showe ba ycen e, es ima ed h ough he cen e-o -g a i y
me hod.
Sou ce: Taken om [3].
dependence o he o e all signal on he beam impac posi ion, due o
channelling e ec s o pa icles inside he op ical ib es, and o he e y
small la e al size o elec omagne ic showe s, ha deposi mos o hei
ene gy in a ew ib es. Wi h an insu icien o a ion o he calo ime e ,
i a pa icle en e ed a ib e, only e y small ene gy deposi s we e le
in o he ib es o he same ype in di e en ows, due o he al e na ing
scin illa ing and Δe enko layou o he p o o ype.
Despi e hese issues, se e al measu emen s could be made wi h his
small-scale calo ime e p o o ype. Fig. 2 shows he elec omagne ic
la e al showe p o ile measu ed wi h 20 GeV posi ons inside he high-
g anula i y module, eaching a millime e p ecision. The a io o ene gy
deposi ed om a dis ance π om he showe ba ycen e, wi h espec
o he o al ene gy deposi , is plo ed. The beha iou is well desc ibed
by he Gean 4-based simula ion mimicking he beam se up condi ions,
including he di e en p o iles o scin illa ion and Δe enko signals.
In ac , in ea ly showe de elopmen s ages Δe enko ligh alls ou side
he nume ical ape u e o op ical ib es, due o i s collima ed di ec ion
wi h espec o incoming pa icles. Conce ning he ene gy measu e-
men s, a good esponse in he whole [10β120] GeV ene gy ange was
obse ed. Howe e , due o he limi ed showe con ainmen ha would
ha e been caused by he a p e-showe de ec o , he ene gy esolu ion
was only es ima ed o ene gies up o 30 GeV. A such low ene gies,
su icien had on ejec ion could be done wi h he ups eam Δe enko
coun e s. Wi h his se up, a s ochas ic e m o 17.5% was es ima ed [3].
Simila esul s we e also ob ained by he same Gean 4 simula ion,
which also sugges ed ha be e esul s could be ob ained by inc easing
he o a ion angle o he calo ime e and he e o e educing he impac
poin modula ion e ec . A s ochas ic e m o 14.5% was ob ained jus
by inc easing he o a ion om 1β¦ o 2.5β¦on he ho izon al di ec ion,
and om 0β¦ o 2.5β¦on he e ical one.
Wi h hese new unde s andings, he same p o o ype was aken
again on he same beamline du ing July 2023 o a mo e in-dep h
cha ac e isa ion. A posi on beam wi h imp o ed pu i y was obse ed,
and he p e-showe de ec o could be posi ioned close o he p o-
o ype, abou 15.5 mm om he calo ime e on ace. A ull angle
scan on he ho izon al di ec ion up o Β±4.5β¦was pe o med, and da a
we e aken wi h wo di e en il ing angles (0, 2.5)β¦on he e ical
di ec ion. Fig. 3 shows he signal modula ion inside in he S channel
( o 20 GeV posi ons) dependency on impac poin posi ion, o he
wo conside ed e ical angles. As expec ed, inc easing he o a ion
Nuclea Ins . and Me hods in Physics Resea ch, A 1069 (2024) 169890
2
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Fig. 3. P elimina y esul s om he 2023 beam es : i shows he mean scin illa ing
channel signal dependence o e he impac poin posi ion, inside he high-g anula i y
module wi h SiPM eadou . A compa ison using wo di e en e ical angles is shown,
using a 20 GeV posi on beam. The ed line shows he modula ion e ec , desc ibed in
de ail in [3]. The blue one shows ha he modula ion can be co ec ly add essed by
inc easing he p o o ype o a ion angle.
Fig. 4. HiDRa modules a e he cons uc ion on he assembly able. A UV lamp was
placed in on o he modules on ace, o see he scin illa ing (ligh blue) and
anspa en (pu ple) ib es ligh collec ed a he ea ace o he calo ime e .
angle allows o sample he elec omagne ic showe in mo e ib es,
and emo e he channelling p oblem, hence educing he dependency
e ec . Ea ly esul s om he analysis o he collec ed da a show ha
a de ini ely imp o ed ene gy esolu ion is in each, despi e some noisy
PMT could esul in highe cons an e m on he o e all calo ime e
ene gy esolu ion. Besides posi ons, da a wi h muons and posi i ely
cha ged pions we e also aken, o es ima e he esponse o he p o o ype
o hese pa icles. Da a analysis is s ill ongoing a p esen .
3. HiDRa had onic calo ime e p o o ype
In o de o assess he pe o mance on had ons o dual- eadou
calo ime e s in associa ion wi h SiPM eadou , a p o o ype able o
con ain had on-o igina ed showe s is unde de elopmen . Simila ly o
he p e ious p o o ype, a modula design consis ing o 80 independen
modules based on s eel capilla y ubes, and al e na ing ows on scin-
illa ing and clea op ical ib es o Δe enko ligh measu emen , is
used. The same cons uc ion echnique, wi h glue illing he olume
be ween he ube ows, has been used. Fo his p o o ype, BCF-12
scin illa ing op ical ib es om Sain -Gobain, gua an eeing longe a -
enua ion leng hs wi h espec o p e ious p o o ype, we e selec ed.
Wi h a c oss sec ion o 65 Γ65 cm2and a leng h o 2.5 me es (abou
10.5 in e ac ion leng hs), he deposi ed ene gy o had on showe s
inside he calo ime e olumes, es ima ed h ough Gean 4 simula ions
in he [10β100] GeV ene gy ange, is a ound 93%. Conce ning he
eadou o his p o o ype, SiPMs will be used o he cen al 10 ou
Fig. 5. Gean 4 simula ion-based expec ed ene gy esolu ion o had on showe s
o igina ed by posi i ely cha ged pions impinging on he HiDRa dual- eadou p o o ype.
o he 80 modules. Two di e en SiPM solu ions, op imised o he
di e en emission spec a and ligh yield o Δe enko and scin il-
la ion emission, ha e been chosen. Fo scin illa ing ib es, a 10 ΞΌm
pi ch model, S16676-10(ES1) om Hamama su, was selec ed, o an
imp o ed dynamic ange due o he la ge ligh yield. Clea op ical
ib es will con e sely be coupled o a 15 ΞΌm pi ch solu ion, S16676-
15(ES1) also om Hamama su, gua an eeing highe pho on de ec ion
e iciency, o cope wi h he low amoun o op ical pho ons emi ed
h ough he Δe enko p ocess. The same Hamama su PMTs ha we e
used o he p e ious p o o ype, R8900 o S channels and R8900-100
o C channels, will be hen used o all o he modules, o scin illa ing
and clea ib es espec i ely, collec ing ligh om 512 ib es each.
Wi h he pu pose o educing he complexi y o he eadou sys em
o he high-g anula i y co e o he HiDRa p o o ype, consis ing o
10240 SiPMs, an analogical sum o eigh adjacen SiPM signals o
he same ype will be implemen ed di ec ly on he on -end boa ds.
The CAEN FERS sys em, which was al eady used o he smalle elec-
omagne ic p o o ype, will also be exploi ed o he eadou o he
SiPM modules: wo FERS boa ds, able o ead up o 64 channels,
will be equi ed o each module. A g ea e o is pu on making
he elec onics and eadou sys ems as compac as possible, he e o e
a oiding he need o an ou he ib es om he back o capilla ies.
The mechanical in eg a ion o SiPMs is in ad anced s a e wi h dummy
componen s, while eal componen s design is almos inalised.
The cons uc ion o he p o o ype s a ed in No embe 2023 a he
INFN labo a o ies in Pa ia, I aly, in collabo a ion wi h o he INFN
g oups. A he ime o w i ing, 33 modules ha e been assembled, some
o which a e shown in Fig. 4. A i s es beam wi h 36 ou o he 80
modules o he ull p o o ype will be ca ied ou a he end o Augus
2024, only using a PMT-based eadou , o a i s cha ac e isa ion and
alida ion wi h had on beams o he p o o ypeβs Gean 4 simula ion.
A ew simula ion-based esul s a e epo ed in Figs. 5 and 6. The
i s one shows he expec ed ene gy esolu ion o single pa icle had on
showe s, aken om a gaussian i o he measu ed ene gy econ-
s uc ed h ough he dual- eadou me hod. A linea sum o he s ochas-
ic and cons an componen s o he ela i e ene gy esolu ion was used
in he i , as a be e ag eemen was ound wi h espec o a quad a ic
sum. Good esul s a e ob ained conside ing he showe pa icles leakage
ou side he de ec o olume mos ly om he sides o he de ec o .
Fig. 6 shows he expec ed spa ial esolu ion o elec omagne ic show-
e s, ob ained as he di e ence be ween he Gean 4 simula ion u h
in o ma ion and econs uc ed showe ba ycen e. An excellen spa ial
esolu ion a a le el o he millime e is ound in he [10, 100] GeV
Nuclea Ins . and Me hods in Physics Resea ch, A 1069 (2024) 169890
3
A. Pa e i
Fig. 6. Gean 4 simula ion-based spa ial esolu ion o posi on-induced elec omagne ic
showe s. Ve y simila esul s a e also ob ained o pho on-induced ones. The combined
esolu ion has been ob ained by weigh ing o he S and C channels esolu ions,
maximising he componen wi h he minimum s anda d de ia ion.
ene gy ange, hanks o he e y high g anula i y o e ed by silicon
pho ode ec o s. The g ouping o 8 ib es in one eadou channel, ha
would be done h ough he on -end boa ds, has been ep oduced
by summing he signals on each independen SiPM. A 5 cm smea ing
on he longi udinal posi ion has been added o he u h in o ma ion
p o ided by Gean 4 on he op ical pho on p oduc ion poin . Such an
in o ma ion, ha in a eal case scena io would be measu ed h ough
iming, is used o co ec he econs uc ed coo dina es o he 2.5β¦
calo ime e angle o a ion on bo h ho izon al and e ical di ec ions
ha is used in he simula ion.
4. Conclusions
Expe imen s a u u e collide s will g ea ly bene i om p ecise
measu emen s o had on je s. The dual- eadou calo ime y echnique
o e s se e al ad an ages o he imp o emen o had on ene gy e-
cons uc ion, while he SiPM eadou o ib es allows u he ad anced
so wa e econs uc ion echniques ha a e unde in es iga ion. Two
dual- eadou calo ime e p o o ypes o his kind ha e been p esen ed:
he i s one, able o con ain only elec omagne ic showe s, has been
cons uc ed and es ed wi h pa icle beams, showing p omising esul s.
The second one, able o con ain had onic showe s, is unde cons uc ion
and will be used o each deep unde s anding o dual- eadou , highly
g anula calo ime e design, in sigh o he calo ime e cons uc ion o
he IDEA expe imen .
Decla a ion o compe ing in e es
The au ho s decla e he ollowing inancial in e es s/pe sonal ela-
ionships which may be conside ed as po en ial compe ing in e es s:
And ea Pa e i epo s inancial suppo was p o ided by AidaInno a.
And ea Pa e i epo s inancial suppo was p o ided by Eu oLabs.
I he e a e o he au ho s, hey decla e ha hey ha e no known
compe ing inancial in e es s o pe sonal ela ionships ha could ha e
appea ed o in luence he wo k epo ed in his pape .
Acknowledgemen s
This p ojec has ecei ed unding om he Eu opean Unionβs Ho i-
zon 2020 Resea ch and Inno a ion p og amme unde GA nβ¦
101004761.
Re e ences
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[2] A. Loeschcke-Cen eno, Simula ion o a capilla y ube, ib e dual- eadou
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[3] N. Ampilogo , S. Come i, J. Aga wala, V. Chmill, R. Fe a i, G. Gaudio, P.
Giacomelli, A. Giaz, A. Ka adzhino a-Fe e , A. Loeschcke-Cen eno, A. Neg i, L.
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Nuclea Ins . and Me hods in Physics Resea ch, A 1069 (2024) 169890
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