Searches for SUSY at the LHC
Searches for SUSY with R-parity conservation are connected with LSP particle - the best dark matter candidate. Using the new Minimal Supersymmetric Standard Model (MSSM) parameters received from recent experimental data at the LHC (CMS) it is possible to calculate the mass spectrum, partial widt...
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irk-123456789-803662015-04-18T03:01:24Z Searches for SUSY at the LHC Obikhod, T.V. Ядерная физика и элементарные частицы Searches for SUSY with R-parity conservation are connected with LSP particle - the best dark matter candidate. Using the new Minimal Supersymmetric Standard Model (MSSM) parameters received from recent experimental data at the LHC (CMS) it is possible to calculate the mass spectrum, partial width and production cross sections of superpatners. In the context of MSSM model histograms of mass distributions for superpartners ~qR and ~g are constructed. Поиски SUSY с сохранением R-четности связаны с LSP-частицей – лучшим кандидатом темной материи. Используя новые MSSM параметры, полученные из последних экспериментальных данных на LHC(CMS), можно посчитать массы, ширины распадов и сечения рождения суперчастиц. В контексте MSSM модели построены гистрограммы распределения масс суперчастиц ~qR и ~q. Пошуки SUSY iз збереженням R-порностi пов'язанi з LSP-частинкою кращим кандидатом темної матерiї. Викормстання нових MSSM параметрiв, отриманих iз останнiх експериментальних даних на LHC(CMS), дає можливiсть розрахувати маси, ширини розпадiв i перерiзи породження суперчастинок. В контекстi MSSM моделi побудованi гiстограми розподiлу мас суперчастинок ~qR i ~g . 2014 Article Searches for SUSY at the LHC / T.V. Obikhod // Вопросы атомной науки и техники. — 2014. — № 5. — С. 3-6. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 11.25.-w, 12.60.Jv, 02.10.Ws http://dspace.nbuv.gov.ua/handle/123456789/80366 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы Obikhod, T.V. Searches for SUSY at the LHC Вопросы атомной науки и техники |
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Searches for SUSY with R-parity conservation are connected with LSP particle - the best dark matter candidate.
Using the new Minimal Supersymmetric Standard Model (MSSM) parameters received from recent experimental
data at the LHC (CMS) it is possible to calculate the mass spectrum, partial width and production cross sections
of superpatners. In the context of MSSM model histograms of mass distributions for superpartners ~qR and ~g are
constructed. |
| format |
Article |
| author |
Obikhod, T.V. |
| author_facet |
Obikhod, T.V. |
| author_sort |
Obikhod, T.V. |
| title |
Searches for SUSY at the LHC |
| title_short |
Searches for SUSY at the LHC |
| title_full |
Searches for SUSY at the LHC |
| title_fullStr |
Searches for SUSY at the LHC |
| title_full_unstemmed |
Searches for SUSY at the LHC |
| title_sort |
searches for susy at the lhc |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2014 |
| topic_facet |
Ядерная физика и элементарные частицы |
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| citation_txt |
Searches for SUSY at the LHC / T.V. Obikhod // Вопросы атомной науки и техники. — 2014. — № 5. — С. 3-6. — Бібліогр.: 11 назв. — англ. |
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Вопросы атомной науки и техники |
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AT obikhodtv searchesforsusyatthelhc |
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2025-07-06T04:20:09Z |
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2025-07-06T04:20:09Z |
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1836869861968445440 |
| fulltext |
NUCLEAR PHYSICS AND ELEMENTARY PARTICLES
SEARCHES FOR SUSY AT THE LHC
T.V.Obikhod ∗
Institute for Nuclear Research, NAS of Ukraine, 03680, Kiev, Ukraine
(Received June 13, 2013)
Searches for SUSY with R-parity conservation are connected with LSP particle - the best dark matter candidate.
Using the new Minimal Supersymmetric Standard Model (MSSM) parameters received from recent experimental
data at the LHC (CMS) it is possible to calculate the mass spectrum, partial width and production cross sections
of superpatners. In the context of MSSM model histograms of mass distributions for superpartners q̃R and g̃ are
constructed.
PACS: 11.25.-w, 12.60.Jv, 02.10.Ws
1. INTRODUCTION
The gauge hierarchy problem and other shortcomings
of the Standard Model (SM) can be resolved by intro-
ducing a spectrum of new particles, that are partners
of the SM particles [1, 2, 3]. These particles may be
neutral, stable and weakly interacting particles that
are good dark-matter candidates. The identity and
properties of the fundamental particles that could be
dark-matter candidates are the most important un-
solved problems in particle physics and cosmology. In
supersymmetry (SUSY) the R parity conservation is
connected with requirement that all SUSY particles
to be produced in pairs and the lightest SUSY par-
ticle (LSP) to be stable. The LSP will pass through
the detector without interacting, carrying away a
substantial amount of energy and creating an imbal-
ance in the transverse momentum. If squarks are
light, their production is enhanced, either through
direct pair production or through production medi-
ated by gluinos, where the latter process is favored
if the gluino production cross section is large. From
Fig. 1 we can see the process described above and
connected with LSP production.
Fig.1. Diagrams of the gluino pair production (left)
and squark pair production (right)
If confirmed experimentally, supersymmetry could
also be considered evidence, because it was discov-
ered in the context of string theory, and all consistent
string theories are supersymmetric. Superstring the-
ory posits a connection between bosons and fermions
and require also the existence of several extra dimen-
sions to the universe that have been compactified into
extremely small scales, in addition to the four known
spacetime dimensions. To ensure the vanishing of the
conformal anomaly of the worldsheet conformal field
theory we must have 10 spacetime dimensions for the
superstring. We will consider the following geometry
of space-time:
R3+1 × C3/Z3 ,
where the six-dimensional additional space is orb-
ifold. Using the correspondence between R3+1 ×
C3/Z3 and AdS5 × S5 spaces and the fact that we
work on additional space, we can graphically and
abstractly represent geometry of the superstring:
Fig.2. Correspondence between C3/Z3 and S5
geometry
From left side of the Fig.2 we have two D-
branes that are described by quivers received
after blow-up of the singularity C3/Z3 (numbers
a, b, c and a
′
, b
′
, c
′
denote orbifold charges [4] char-
∗Corresponding author E-mail address: obikhod@kinr.kiev.ua
ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2014, N5 (93).
Series: Nuclear Physics Investigations (63), p.3-6.
3
acterizing McKay quivers) and open superstring is
described by Exti groups determined by the dia-
gram [5]. On the right part of Fig.2 we can see
the Schwarzschild geometry that is connected with
Friedmann universes of positive and negative spa-
tial curvature and is the geometry of the spacelike
hypersurface [6].
2. PARTICLE CONTENT AND MASS
SPECTRUM OF SUPERPARTNERS
The moduli space of an open superstring [5] has the
form
Ext0(Q,Q
′
) = C aa
′
+bb
′
+cc
′
,
Ext1(Q,Q
′
) = C 3ab
′
+3bc
′
+3ca
′
.
(1)
Substituting in (1) orbifold charges
a = b = c = a′ = b′ = c′ = 4
and using the Langlands hypothesis [7], we obtain the
realization of (1) in terms of SU(5) multiplets:
3× (24 + 5H + 5H + 5M + 5M + 10M + 10M ) .
This result determines the particle content of the
MSSM. The gauge invariant MSSM superpotential
takes the form:
WSU(5) = λd
ij · 5H × 5
(i)
M × 10
(j)
M +
+λu
ij · 5H × 10
(i)
M × 10
(j)
M + µ · 5H × 5H ,
(2)
where 5H and 5H are Higgs multiplets, 5
(i)
M and 10
(j)
M
are multiplets of quark and lepton superpartners,
λd
ij , λu
ij are Yukawa coupling constants and µ is the
Higgs mixing parameter.
Using the restricted parameter set in (2), received
from the recent experimental data [8]
M0 = 800 GeV , M1/2 = 650 GeV ,
A0 = 0 , tanβ = 10 , sgn(µ) = +1
(3)
it is possible to calculate the mass spectrum of su-
perpartners by application of the computer program
SOFTSUSY [9]. This MSSM spectrum is shown in
Table 1.
Table 1. Mass spectrum of superpartners
GeV GeV GeV
ũR 1499 g̃ 1498
ũL 1539 ν̃e 901 χ̃0
1 273
d̃R 1495 ẽR 834 χ̃0
2 516
d̃L 1541 ẽL 905 χ̃0
3 792
c̃R 1499 χ̃0
4 805
c̃L 1539 ν̃µ 901 χ̃±
1 516
s̃R 1495 µ̃R 834 χ̃±
2 805
s̃L 1541 µ̃L 905
t̃1 1138 h0 117
t̃2 1411 ν̃τ 898 A0 1188
b̃1 1389 τ̃1 825 H0 1188
b̃2 1487 τ̃2 902 H± 1191
3. PARTIAL WIDTHS AND LSP
Using the parameter set (3) it is possible to calcu-
late partial widths of superpartners by application of
the computer program SDECAY [10]. These partial
widths are shown in Tables 2, 3.
Table 2. Partial widths of superpartners
channel BR channel BR
ũR χ̃0
1u 0.997 χ̃0
4u 0.002
d̃R χ̃0
1d 0.997 χ̃0
4d 0.002
c̃R χ̃0
1c 0.997 χ̃0
4c 0.002
s̃R χ̃0
1s 0.997 χ̃0
4s 0.002
Table 3. Partial widths of superpartners
channel BR channel BR
g̃ b̃1b
∗ 0.074 t̃1t
∗ 0.425
b̃∗1b 0.074 t̃∗1t 0.425
From Fig.1 we can see that after the pp reaction
each member of the produced pair initiates a de-
cay chain that terminates with the lightest SUSY
particle (LSP) and SM particles, typically includ-
ing jets (one for squark and two for gluino). This
fact can be proven with the help of Tables 1 and 2.
From Table 1 we know that lightest SUSY particle
is neutralino (χ̃0
1 = 273 GeV) and from Table 2 we
can see that all SUSY particles decay through the
channel q̃R → q + LSP . If the LSP only interacts
weakly, as in the case of a dark-matter candidate,
it escapes detection, potentially yielding significant
missing transverse energy (Emiss
T ).
4. CROSS SECTIONS
Using the parameter set (3) it is possible to calculate
production cross sections of superpartners by appli-
cation of the computer program PYTHIA [11]. These
cross sections at center-of-mass energy
√
s = 14 TeV
are shown in Table 4.
Table 4. Cross sections of superpartners
channel cross section, pb
gg → g̃g̃ σg̃g̃ = 0.139
qg → d̃Rg̃ σd̃Rg̃ = 0.153
qg → ũRg̃ σũRg̃ = 0.341
qq
′ → ũRd̃R σũRd̃R
= 0.173
Analysis of the calculated data presented in Table 4,
leads us to the conclusion that gluino production pro-
cess is one of the four favored processes as was em-
phasized in introduction.
4
5. RECONSTRUCTION OF MASSES
To construct histograms describing mass distri-
butions for superpartners q̃R and g̃ we choose
the set of parameters (3). Using this param-
eter set it is possible to construct histograms
of mass distributions for superpartners by appli-
cation of the computer program PYTHIA [11].
This histograms are shown in Figs.3 and 4.
Fig.3. Histogram of mass distribution for q̃R
Fig.4. Histogram of mass distribution for g̃
6. CONCLUSIONS
Whereas more than 80% of the matter in the universe
remains invisible deciphering the nature of this ”dark
matter” remains one of the most interesting questions
in particle physics. The CMS collaboration recently
conducted a search for the direct production of dark-
matter particles (χ), with especially good sensitivity
in the low-mass region. An important aspect of the
search by CMS is that there is no fall in sensitivity for
low masses. After event selection, 3677 events were
found in the recent analysis. CMS has set limits on
the production of dark matter, as shown in the Fig. 5
of the χ-cross-section versus χ mass.
Fig.5. χ cross-section versus χ mass
The limits show that CMS has good sensitivity in
the low-mass regions of interest. Our calculations of
neutralino masses as shown in Table 1 are in agree-
ment with the last experimental data received from
the LHC (CMS).
References
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tions in Four Dimensions// Nucl. Phys. 1974,
v.B70, p. 39-49.
2. H.-C. Cheng and I. Low. TeV Symmetry and the
Little Hierarchy Problem // JHEP. 2003, v.09,
p. 1-51.
3. T. Appelquist, H.-C. Cheng, and B. A. Dobrescu.
Bounds on Universal Extra Dimensions // Phys.
Rev. 2001, v.D64, p. 035002-035011.
4. M.R. Douglas, B. Fiol and C. Römelsberger. The
spectrum of BPS branes on a noncompact Calabi-
Yau // JHEP. 2005, v.09, p. 1-57.
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6. C.W. Misner, K.S. Thorne and J.A. Wheeler.
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San Francisco, 1973, 519 p.
7. W. Schmid. Homogeneous complex manifolds
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try in final states with missing transverse energy
and 0, 1, 2, or ≥ 3 b-quark jets in 7TeV pp col-
lisions using the variable αT // arXiv:1210.8115
[hep-ex].
5
9. B.C. Allanach. SOFTSUSY2.0: a program for
calculating supersymmetric spectra // Comput.
Phys. Commun. 2002, v.143, p. 305-331.
10. M. Muhlleitner, A. Djouadi and Y. Mambrini.
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ÏÎÈÑÊÈ SUSY ÍÀ LHC
Ò.Â.Îáèõîä
Ïîèñêè SUSY ñ ñîõðàíåíèåì R-÷åòíîñòè ñâÿçàíû ñ LSP -÷àñòèöåé � ëó÷øèì êàíäèäàòîì òåìíîé ìà-
òåðèè. Èñïîëüçóÿ íîâûå MSSM ïàðàìåòðû, ïîëó÷åííûå èç ïîñëåäíèõ ýêñïåðèìåíòàëüíûõ äàííûõ íà
LHC(CMS), ìîæíî ïîñ÷èòàòü ìàññû, øèðèíû ðàñïàäîâ è ñå÷åíèÿ ðîæäåíèÿ ñóïåð÷àñòèö.  êîíòåêñòå
MSSM ìîäåëè ïîñòðîåíû ãèñòîãðàììû ðàñïðåäåëåíèÿ ìàññ ñóïåð÷àñòèö q̃R è g̃.
ÏÎØÓÊÈ SUSY ÍÀ LHC
Ò.Â.Îáiõîä
Ïîøóêè SUSY iç çáåðåæåííÿì R-ïîðíîñòi ïîâ'ÿçàíi ç LSP -÷àñòèíêîþ � êðàùèì êàíäèäàòîì òåìíî¨
ìàòåði¨. Âèêîðìñòàííÿ íîâèõ MSSM ïàðàìåòðiâ, îòðèìàíèõ iç îñòàííiõ åêñïåðèìåíòàëüíèõ äàíèõ íà
LHC(CMS), ä๠ìîæëèâiñòü ðîçðàõóâàòè ìàñè, øèðèíè ðîçïàäiâ i ïåðåðiçè ïîðîäæåííÿ ñóïåð÷àñòè-
íîê.  êîíòåêñòi MSSM ìîäåëi ïîáóäîâàíi ãiñòîãðàìè ðîçïîäiëó ìàñ ñóïåð÷àñòèíîê q̃R i g̃.
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